the sofa will have a pull out bed, while a couch will not. While a sofa and couch may in all practical purposes be one in the same, the small differences could easily be a determining factor when it comes to cost of the piece.
The term couch is in reference to a long piece of furniture that is larger than a love seat, generally seating three folks on it comfortably. It can come in many styles including Victorian, colonial, or modern decor. A couch is a very important piece of furniture as it gives more seating room should you have more guests over than you anticipated.
A sofa, on the other hand, can be longer than your average couch, sometimes seating up to four folks at one time. Many of the newer sofas are even equipped with a pull out bed. These sofas are known as a couch sofa bed or a couch sleeper sofa.