a long arm is a large sewing machine with much more (throat-space) than your regular machine. there are a number of different companies and many different price ranges. there are gammils, handiquilters, nolting, apqs machines...the list goes on and on. with all kinds of different features, stitch regulators; laser's, design features.
if you are looking into something like this it is really recommended to go to as many dealer's shops as possible and try them out. it is a very big investment and you want the one that works best for you and falls into your price range.
if you are simply looking for a quilting frame to use your home machine on there are a number of those companies too...there are flynn's, gracie's, hinterburgs...again the list goes on.