Brake horsepower (bhp) is the measure of an engine's horsepower before the loss in power caused by the gearbox, alternator, differential, water pump, and other auxiliary components such as power steering pump, muffled exhaust system, etc. Brake refers to a device which was used to load an engine and hold it at a desired rotational speed. During testing, the output torque and rotational speed were measured to determine the brake horsepower. Horsepower was originally measured and calculated by use of the "indicator" (a James Watt invention of the late 18th century), and later by means of a De Prony brake connected to the engine's output shaft.
In the US, car's HP is rated at SAE net so as to give a truer value of HP available at the crankshaft. SAE net is the HP output of the engine after the alternator, waterpump, power steering, etc., are added to the vehicle. Automotive manufacturers used to use SAE gross, which is BHP equivalent. This gave a misrepresentation of what the owner could expect from the vehicle as far as performance. This all came about during the HP wars of the 60's and 70's.
EDIT: (realized I didn't answer the second part of your question)
Also, from Wikipedia:
Torque, moment or moment of force, is the tendency of a force to rotate an object about an axis, fulcrum, or pivot. Just as a force is a push or a pull, a torque can be thought of as a twist to an object. Mathematically, torque is defined as the cross product of the lever-arm distance and force, which tends to produce rotation.
In the automotive world (or bike world in your case), torque is the force which gets your bike moving. The more torque, the quicker the bike can move. You will usually hear two different terms: torque and horsepower. Torque is the twisting force; mechanical horsepower is a number derived from the equation
- HP = Horsepower
- RPM = Rotations Per Minute (engine speed)
- T = Torque
HP is usually considered the force which keeps the vehicle moving. HP the rate at which work is done.