Welcome to the world of strings. For every brand of tennis racquet there is probably 10 brands of string available. All promise that you will perform better than Roger, Novak , Andy or Stan but the real key is matching player, racquet and string together with tension to come anywhere near that promise. Some players are after feel or softness perhaps trying to recover fro injury whilst competition players are often pushing the boundaries of power and spin and often looking for durability. In simple form there are 4 main types of strings but many sub types. Nylon, Multifilament, Polyesters and Natural gut are broad categories with many sub types within each. Taking in to account you, your style of play, your equipment and the types of opponents you face an experienced racquet technician will help you arrive at a great recipe quite quickly.