Originally Posted by Dan
Horsepower isn't just some number. It's just a little more difficult to explain than torque is. The fact that there are several units of measurement that can all be referred to as "horsepower" also makes things a little more confusing. http://en.wikipedia.org/wiki/Horsepower
Horsepower is a measurement of power. Power is work over time. Work is a force times a distance.
Hook your truck up to a house, and floor it (we'll pretend for this example that your tires are awesome and don't spin at all- just put everything your engine puts out to the ground). You won't go anywhere, but you will generate plenty of torque. Since you haven't gone anywhere, you will have generated 0 horsepower though since you need to travel some distance in order to have done any work, and if you haven't done any work, you haven't generated any power.
lol...I know its not just a number...but, everyone goes around saying, "I have xxx whp!" But, while they do, are only generating miniscule torque...
Torque is what gets you moving, horsepower is what keeps you there. Without torque you have nothing...though, without hp, as you said, your have nothing either....so, the trick is, to find a happy medium.
Good explaination though