Do you reuse cloth diaper plastic covers after each changing or are you suppost to use a new one every time?

I'm thinking about using cloth diapers, but I'm having a little trouble figuring everything out. I've found websites that tell you all about the different cloth diaper system. What I don't understand is when you use a prefold diaper and a plastic cover, can you reuse the plastic cover if you wipe it out or are you suppost to use a new cover every time you change your baby? I think using prefolds will be an easy way to start using cloth diapers until I can build up a nice stack of others like all-in-ones or something!!! Please help!