The pull-out sofa bed does exactly what it's sounds like. The top cushions are removed from the couch and placed to the side. Underneath them is a spring-loaded metal frame. The bed is pulled out from the center and flipped forward with three folding sections. The bed frame snaps into place and pairs of legs automatically come down to support the mattress. The mattress is usually about half the thickness of a standard bed mattress.
A futon sofa bed is also known as sleeper sofa or lounge. The hinge on the sofa is released and the back-support cushion slides out to create the bed. Futons are usually made of a thin mattress pad material, but larger, slide-out couches have been manufactured using the futon mechanics. Throw pillows provide a head rest when used as a bed.
Instead of removing cushions every time, you can use a drawer-style sofa bed. The bed mechanism is underneath the couch. Pull out the drawer under the couch. The bed pulls up and the legs fold out and rest on the drawer. An extended side of the couch adds to the size of the bed and provides an extra seat when the bed is not in use. All of the cushions remain in place on the couch.
The electronic bed uses button controls to transform the couch into a bed. Generally, the first button slides out the front cushions of the couch several feet. The second button automatically slides up two additional cushions to create the bed. This is essentially a longer couch with the backrest and cushions still intact on the couch.