Since the 1950s when longboarding began it has undergone many changes and innovations. Not all the riders were content with just the one kind of cruising. Some started to race downhills and found a need for a different kinds of board shapes and wheels. Some started to slide meaning they needed softer wheels and a different board to increase their stability while in the slide.
Some need very long boards so that they can walk around on them. This is called dancing. For whichever activity you are going to be using your board, there are more than enough varieties for you to choose from.