After Effects --> Compositing
Premiere Pro --> Editing
Flash --> (interactive) Web authoring
Lokk up those terms in a web search. And sure, there's some overlap and always has been just liek their will be overlap with general graphics manipulation in Photoshop, but really, this is nothing anyone can explain in 5 minutes. I recomemnd you realyl try to visit a media arts school or a production facility and sit in for a few hours to understand some basic concepts and differences.