Someone who is cultured and polite — who knows to put his dinner napkin on his lap — is civilized. So could you please behave in a civilized manner and get your feet off the dinner table?
Civilized is an adjective that describes the very opposite of barbarity. A civilized person is polite and courteous; he knows how to say "please" and "thank you." A civilized group of people is characterized by being socially and technologically advanced. Both dinner parties and fancy computer gadgets are signs of a civilized people. That friend of yours who likes to show people how he can belch the entire alphabet? Maybe not.