flip doesn't do anything else than glswapbuffer -> swap front and backbuffer. ( you might check the sources yourself. I crawled them last night in hope to find out how drawimage works ... nothing so far but I create a C function that gives me the hwnd for some other winapi stuff like waitevent etc ;) )
the draw is the actual work where the whole thing is drawn into the backbuffer
the draw is the actual work where the whole thing is drawn into the backbuffer