Sofa VS Couch

When I was in Canada, I heard most people say 'couch' to mean 'sofa', actually, i never heard Canadians use 'sofa'. Is sofa an outdated word? Or is this a Canadian thing? Which word is used in US or UK?

The Cambridge Advanced Learner's Dictionary give couch this definition:

couch (SEAT) http://dictionary.cambridge.org/define.asp?dict=CALD&key=17492&ph=on
noun [C]
a http://dictionary.cambridge.org/define.asp?key=75477