If a man grows strips of hair on his face from his hairline above the ears to just below them, they're called sideburns. If your sideburns cover your chin, they're not sideburns; that's a beard!
Sideburns owe their name to an American Civil War general, Ambrose Burnside, whose distinctive facial hair came to be called burnsides. The word was flipped sometime during the 19th century, becoming sideburns. If you want to see a famous set of sideburns, check out pictures of Elvis.