So first off, Photoshop uses pixels (bitmaps) and Illustrator uses equations (vectors). In Photoshop your basically just cutting and pasting images together. If you enlarge them, you start to see the pixels. In Illustrator, you just ‘draw’. You can add in images and trace over them. Editing is extremely different between the two. In Photoshop, one you do something, its done. It takes forever to fix things (if at all) and they don’t turnout very nice some times. But In illustrator, since everything is an equation, you can fix things in a very quick and simple manner, without changing the quality.
(my computer wasn’t working, ill finish later)