There are primarily 4 kinds of skis that you will want to consider when choosing waterskiing equipment. They are: combination, slalom, trick and jump. The most common type are combination, followed by slalom and then trick and jump skis.
Combination skis are designed for typical recreational skiing with wider tips to make them easier to control and easier for beginners to get up. But they are preferred by many advanced skiers also. The reason they are called combination skis is that one of them typically has a double foot binding so that it could be used as a slalom ski. Combination skis are great for beginners who eventually want to do some more advanced skiing later on.
Slalom skis are designed for speed and maneuverability. These are typically used by journeyman skiers up to those who are experts. As already mentioned, a slalom ski has two foot bindings and are used as a single ski. That makes them a bit less stable and they require more skill, but they make up for that with high performance. Wider slalom skis are designed for intermediate use, as the wide stance makes it easier to get up and balance. More professional slalom skis will have beveled edges, a more concave bottom shape, and a tapered tail. These changes make them harder to use, but also allow for spectacular speed and cornering performance.
Trick skis are built to accommodate those who want to do spins and various other tricks on the water. They are typically shorter than other skis and do not have any fins for stability. They are inherently unstable which is a good thing if you are going to spin and slide through the wake. As you might expect, these types of skis are for more experienced skiers only.
Jump skis are designed specifically for use on ramps. When you look at jump skis you might think they look a little old fashioned since they are longer and wider than most others, but they are actually engineered with special composite materials to be strong and light. This special construction is important when you consider that they must endure sliding along a ramp as well as water. You probably want to have quite a bit of waterski experience under your belt before you try ramp jumping!