Help me understand power supply terminology

Really new to power supplies, and thought I would ask a few newbie questions

What is a watt and how does it compare to a volt? An Amp?
What does -12V mean?
What is a rail?

I am concerned with how a wall outlet fits into the power scheme. You can have a power supply rated for 700w, but if it doesn't have a wall outlet that can provide that, it can't get 700w, can it? Or am I mistaken here?

How can I tell how much power my outlet provides?
Does an outlet with two plugs provide power equally to the two plugs, dividing the power supply in half?
Is the power an outlet supplies divided by the other outlets in a house?

Thanks for any and all help.

wth?? the outlet can supply the power as long as your circuit breaker can support the amp/watts drawn

ok.. ok.. umm.. stop with the power outlet equalling/dividing/halfings.... go back to my first sentence

The 700 watt PSU doesnt actually feed 700 watts to your components - It feeds as required.. there the effeciency factor that comes into play. 80% effeciency are standards..

Google is your friend.