I call it a couch.

My parents called it a couch, and we had a big, ugly orange and white velveteen one growing up, that all our friends and us sat on, jumped on the cushions and watched TV on.

However, my grandparents did not have a "couch" they had a "sofa" or a "davenport". We would no more have sat on those things than we would have thrown oatmeal on the carpet.

Perhaps it's a level of formality, perhaps it's generational.