Experience Points: A Few Questions

[Belts]

I haven't seen these questions anwered yet, so if they have been, I apologize.

Does experience depend on your level, or the level of the monster? Like, if you are a low level and you kill a higher level monster, do you get more experience? And vise versa, if you are a high level and you kill a low level monster, do you get less/no experience?

Also, say the levels of your party vary greatly (like there is a level 2, 12, 34, and 49.) Because it is much easier for the lower levels to kill things, due to the fact that they have high level characters helping, do they get less experience because they aren't really doing much?

The reason I ask is because me and my girlfriend are going to be playing this together. On some days I can play a lot more than her, so I may get a bit ahead of her. Would I be able to help her catch up, or would she get crappy experience because I am higher than her?

Thanks in advance! (I hope those made sense.)

[Ether]

Exp is entirely determined by the monsters type and level, a players level doesn't factor into it

[Belts]

Oh, ok. That's a lot different from what I am used to. (FFXI)