Elements… is a stripped down version of their other programs. “Photoshop Elements” can be translated “Photoshop with all the good stuff taken out”. Don’t waste your time.
Illustrator… is for illustrating. It’s not the same as Photoshop at all. It focuses on drawing tools and suchnot for people who do graphic design or illustration.
InDesign is for page layout. Brochures, pamphlets, publications, etc. although I’ve always felt that InDesign was inferior to the program it was intended to replace - PageMaker. The ULTIMATE layout program is FrameMaker, but that’s very VERY expensive.
AfterEffects is … for motion graphics. Animations and the like.
InCopy is part of their “collaborative workspace” thing, it’s for allowing a whole bunch of people to edit documents. Frankly, I dislike Adobe’s entire “workspace” concept, although it IS, I suppose, a step in the right direction.