Al's explaination of TE and HP is great. I just want to add definitions of 3 terms that are often related and confused.
Force - The amount of push or pull measured in pounds or newtons (1 lb = 4.448 n).
Energy (or work) - A force acting thru a distance measured in foot-pounds or newton-meters (1 ft-lb = 1.356 Nm).
Power - The rate of doing work or of expending energy measured in horsepower or watts (1 hp = 746 watts).
Bob Weber