http://www.yawpower.com/tqvshp.html ~~ Very good website with great explanation
http://www.vettenet.org/torquehp.html ~~ Another good website

TQ is the "strength" of an engine.
RPMs are how many times your engine applies it's TQ.
HP is both measured together.

TQ is basicly a function of displacement (natural or artifical). The more air and fuel you get in at one time the stronger the engine. In a n/a engine having a larger displacement engine limits how fast it can turn (RPM) simply because the pistons have further to travel. [Piston speed]

Now RPMs are basicly how many times your engine moves (or is moving) it's displacement (keep in mind power and exhaust strokes).

Tq and rpm (in a overall sense) are basic opposites, you give up one for the other. Either you move more air at one time or you move less air more times. Horsepower just tells you the end result.