Golf balls are differently built, some are very simple others are more complex. To get an easy picture about the structure of today's golf balls, we would like to explain the basics as follows:

In early times golfers made out that irregularities in the surface of the ball would let the ball fly higher and farer. Soon, right after the Gutta Percha balls the so called dimples were purposely printed into the surface of each ball. Still nowadays, most of the ball manufacturers are testing out different shapes and numbers of dimples. The rule goes: the more dimples a ball has, the higher it goes. Then, balls having too many dimples, do fly too high and are lacking distance. Most companies have found their best number of dimples, mostly they are ranking between 300-500 per ball.

Technical background:
Well hit golf balls go about 200 km/h (120 m/h). Once off the tee, the ball starts to slow down because because air is sticking to it while flying, just like water sticks to a ball if it falls into water. Since air is sticking to the surface it streams over, it makes sense that the less area on a ball, the less sticking and the less drag there is to overcome.
It looks obvious that a smooth coating on a polished sphere would go farther than a ball with a roughed, lemon skinned surface. But, at the speed that golf balls go, it doesn't quite work that way.

Imagine to be a tiny entity, perhaps the size of a micro crustacean - small enough to fit between grains of sand. Now imagine to ride on the surface of a golf ball in flight, or in the wind tunnel at the lab. You realize that right at the surface of the ball, the air is still and it sticks to the plastic as the air molecules are dragged along like syrup running from the rim on a little pitcher at a popular pancake breakfast place. But getting away from the surface, say as far as the thickness of three sheets of paper, we notice that the air is going full speed. Here we're in, what we in golf science call, the "free stream" which moves at 200 km/h.
However, the air streaming over a golf ball forms a "boundary layer" of relatively slow moving air. It's distinct. Right at the surface, the air is stuck. A millimeter away from the surface, the air is going full blast. In between - in the boundary layer - it's just slurping along.

That slow moving air in the boundary layer is a source of drag. It lets the air stick to the surface and tumble behind the ball in wild whipping whirlpools. The energy in the boundary layer is lost energy. The tumbling air behind the ball allows a large (relatively large, it's just a golf ball) region of low pressure to form, creating a partial vacuum that would suck the ball back toward the tee. So, the thinner the boundary layer, the less slurpy drag there is, and the sooner the air behind the ball can get back up to the "free stream" speed. The less drag, the farther the ball will be driven.

Here's where the dimples do their job. Dimples make the molecules in the layer tumble. They start roiling against one another. The boundary layer becomes "turbulent." The molecules in the layer are no longer just sliding across the surface gently jostling. Now, they're rolling and bouncing and bumping each other along. When the molecules are in a turbulent boundary layer, they're moving closer to the free-stream speed. There is less of a difference between the speed of the tumbling molecules and the speed of the ball.

It turns out that the air flow in a turbulent boundary layer on a dimpled golf ball is thinner than a smooth or "laminar" flow on, say, a ping-pong ball. Boundary layers are laminar or turbulent, or somewhere in between. We say they're in "transition." Dimples make the transition quick-- not a smooth transition, a turbulent one, ha! (A little fluid dynamics gag there...) When the layer is turbulent and thin, the ball loses less energy to the free stream air. And, drag is lower. Isn't that weird? The dimples make the ball develop less drag.

Some balls are indicated with a compression of 80, 90 or 100 etc. Originally it was used as a measurement for quality of 3-piece balls, where a long rubber was streched arround the core. The rubber had a lenght of approx. 20 meters and was streched at a factor of approx. 20 times of its original, depending on the compression that is wanted. This way it is wounded arround the core. It was said that the tighter the windings, the better the ball performed. This created a long-standing perception that compression affects golf ball distance and performance.
Because golf ball technology uses newer heat-resistant threads with newer and better winding equipment for three piece balls, golf ball compression has become merely a condition of feel. Now with the availability of the consistent quality of a two piece ball, compression as a measurement of quality is rather obsolete.

Definition: Today the word "compression" in the golf ball industry relates to a value expressed by a number in the range from 0 to 200 that is given a golf ball. This number defines the deflection that a golf ball undergoes when subjected to a compressive load. Compression simply measures how much the shape a golf ball changes under a constant weight.

Measurement: All three-piece balls and some two-piece balls are measured for compression. A ball that doesn't compress is rated 200; a ball that deflects 2/10ths of an inch or more is rated zero. Between those two extremes, for every 1/1000ths of an inch that the ball compresses, it drops one point from 200 and the compression rating is then established.
Most balls have compression ratings of either 80, 90, or 100; the lower the compression, the softer the feel. Not every ball marked 80, 90, or 100 is exactly that rating. The actual rating can fall roughly within 3-5 points on either side of the indication. Any ball that falls out of this range is usually sold as range ball, or as X-outs.

Prove: There have been several published texts to prove that golf ball compression relates more to feel and your own superstition than its performance. The conclusions were, if you take different rated golf balls which have the same construction, aerodynamics, and cover material, and use an automatic golf swing machine such as the Iron Man, the yardage difference between the balls hit were negligible, less than two yards.

The covers of today's golf balls are made of numerous different materials such as Balata, Surlyn, Zylin, or Elastomer. The main challenge is to find a cover, that provides a sensitive, soft feeling for the ball while hard enough not to be cut still after thousands of shots. Therefore, ball manufacturers have special machines shooting the ball against a wall with a speed of more that 250 km/h.

Balata: as a type of natural rubber and the softest of all other cover types, Balata is less cut resistant. However, with all other aspects of construction being equal, a balata-covered ball will spin easier and is preferred by players who demand maximum feel and control. This means more control over shots where the action of the ball is critical.

Surlyn: Surlyn was the first and most durable cover material that revolutionized the construction of the golf ball when it was introduced in the early 80's. It is a trade name for a group of thermoplastic resins developed by the Dupont Corporation. Most manufacturers of durable covers use either Surlyn or a similar material blend. The emphasis today is to provide both durability and feel.
This durable cover offers better cut and abrasion resistance than the balata cover. A Surlyn covered ball generally feels harder than balata covered balls. The hardness of this cover material accounts for a lower spin rate.

The deciding factor for most golfers is economics: many of today's regular golfers have turned to durable covered balls simply because they know an occasional miss-hit won't cut the cover.

Choosing a golf ball we mostly find information on the box mentioning to be a 1-, 2-, or 3-piece ball. In simple words, the explanation is as follows:

1-piece balls	This ball is seldom used as a playing ball. It is a good ball for beginners, cheap in its production, and mostly used on driving ranges. It is typically made from a solid piece of Surlyn with dimples molded in. It is inexpensive and very durable. On impact with the club face, the one-piece ball has a softer feel.
2-piece balls	A Two-Piece golf ball is used by most ordinary everyday golfers because it combines durability with maximum distance. These balls are made with a single solid core (usually a hard plastic) enclosed in the ball's cover. The solid core is typically a high-energy acrylate or resin and is covered by a tough, cut-proof blended cover that gives the two-piece ball more distance than any other ball. These "hard" balls are covered in either Surlyn, a specialty plastic proprietary to the Du Pont Company, or a similar kind of material. The two piece is virtually indestructible and with its high roll distance, it is by far the most popular golf ball among ordinary golfers.
3-piece balls	Three-Piece golf balls or wound balls have either a solid rubber ore liquid center (core) which is covered by many yards of elastic windings, over which is molded a cover of durably Surlyn, Surlyn like, or balata. Wound balls are softer and take more spin, allowing a skillful golfer more control over the ball's flight when hit. It typically has a higher spin rate than a two piece ball and is more controllable by good players. A Surlyn cover is a thermoplastic resin that is harder than a balata and is considerably more durable. A balata-covered, liquid centered, three piece ball takes longer to manufacture than a two-piece ball. The wound construction over a liquid center, combined with a soft synthetic balata cover, produces a very high spin rate, providing maximum control and feel.
4-piece balls	The 4-piece ball is a newer form of the original 3-piece ball.

Seen with the eyes of an ordinary golfer sizes of golf balls have hardly changed throughout the ages. Nevertheless, there are and have always been differences in sizes, in the recent years mainly two sizes. Before the 1980's the common size was 1.62 inches (4,11 cm), while soon after the size of 1.68 inches (4,27 cm) was standard. Nowadays, in tournaments there is only the standard size of 1,68 inches allowed and in shops there is generally no other size available.

Going through history, golf balls had quite irregular weights. While the feathery balls were less standarized the weights were becoming standarized with the beginning of the gutta percha balls. Nowadays, golf balls are ranking between 41-47 gramms, including those being produced still in the 70ies. The everage weight would be arround 45gr.
One exeption is the Cayman ball, constructed by Jack Nicklaus in the 80ies. This ball only weights half of the standard weight (approx. 20 gr.) to enable less distance for smaller golf courses.