You know, the answers are included in the helpfile F1 ... but since they are so cryptic ... and this is very important stuff u need to understand BEFORE the rest makes any sense :
1. mc is short for movie clip
2. a- A graphic is a static image/animation. It can be set to loop, but is not used for dynamic stuff.
2. b- A button is ... a button. Use these to let the user interact with your movie.
2. c- A movieclip (mc) is a smaller version of a movie if u'd like. It can contain graphics, buttons, textboxes, other mc's and even swf's. Use these if u want to be able to interact with anything or change stuff at runtime.
3. The up state is how your button looks by default. The over when you roll your mousepointer over it. The downstate when u click the button and the last is the hit area of your button. If u only fill the last, u have an invisible button, which can be clicked, triggerd etc.
I suggest u read a couple of our tutorials here

. Also, read the forum rules. Thread titles need be helpful.

Good luck ! Let us know when things are unclear.