Question about the reputation system

Im not sure if this is the right place for a question of this type, but every time I search for answers to these questions I just find posts saying where the button to give rep is at. If anybody has a link to a thread that answers this feel free to close this thread ^_^.

Do the people I +rep to see the message I typed, and who I am?
Is it just a pat on the back, or am I "sacrificing" my own rep for it (the whole "spreading rep around" thing.)
Lastly, is it post specific or user specific? For instance if 3 grow faqs helped me and i rep the creators of all 3, and two were written by uncle ben, would he still get two +rep hits from me or is it a "one per person" sort of thing.

Thank you very much for reading this!

Wow, actually thanks to the threads at the bottom of the page "that ae similar" I found a couple answers. So it seems that they see the message, but not the user that typed it unless they are an elite society member? Also I read that you can give negative rep but I don't see a button for it. Is that the "report post" button? Lastly, what is the difference between the filled and unfilled boxes in the members with high rep? I've seen people with several of each, and others only with filled boxes.

These are all good questions i would like the answers to as well. Does me giving rep take away my rep?