A video card is what your computer uses to display things on your monitor, so if you are reading this you have a video card.... Now a video accelerator is probably a 3d add-on card, witch works in union with you 2d card... and are for running 3d game ect. This is what you need if it says Hardware acceleartor needed, you need a voodoo or voodoo 2 card... So video card you have, accelertor, you buy.....
Does this help?
Actually "video accelerator" is a term that first appeared with 2d only cards way back when Windows was in its infancy. This is an indication that the card has built in instructions to run GUI (graphical user interface) applications faster, ie: accelerated. Nowadays, all new video cards sold are 2d accelerators that will enhance the speed of windows opperations. Most are also 3d accelerators that enhance 3d games (alot of the older ones are really bad at it though, and nicknamed 3d decelerators). A "video card" is just that. A card that outputs processed data (video) to your monitor without any special enhancements.