enchanting an item adds a "bonus" to it. A level 51 item can have a 35% bonus to it. This bonus factors in to "to-hit" calculations, although I'm not sure exactly how. You should always try to get your weapons, shields and armor enchanted. Most drops already are enchanted, but player made stuff will need to be done. For early level stuff, when you go through armor so fast, it probably is not necessary to get this done, but if you are higher level, it does help some.