body perm -- help!

Hi. I have medium length dirty blond hair and it's somewhat wavy and thick, although i straighten it with phytodefrisant and a hair dryer every day. Anyway, i'm relatively happy, except that until recently , i always thought perms were to make hair curly, but learned of somethign called a body perm or permanent wave, which add body to hair. I'm totally ignorant on the subject i must admit, has anyone had these done? Have I been missing out on somethign for years? Will these offer me more control and volume? Is it just one big roller stuck in your head or something? Any details are appreciated. Thanks!