A sub-genre of Rock & Roll. Classic Rock is roudy and sexual enough to be Rock & Roll, yet retains much blues inluence and song structure. (Rock was pretty much created from Blues.)
Classic rock was popular throughout the '60s and '70s and then mostly dissappeared in the '80s; replaced with Hair Metal, for some reason which I've yet to understand, as Hair Metal is simply awful.
All of Rock's best guitarists are Classic Rockers. (Jimi Hendrix, Eric Clapton, Carlos Santana, Jimmy Page, Stevie Ray Vaughan, David Gilmour, etc. etc.)
I used to listen to the stuff you hear on the radio, but my dad introduced me to some awesome old Classic Rock bands.