Well Kend, in simplest terms, the camshaft is the 'brain' that tells the engine intake and exhaust flow what to do and when.
It delegates how and when each valve opens and closes, and is a 'science' everyone is looking for to find the optimum efficiency for their component package throughout the entire rpm range.
Your choice of camshaft should be the most logical design and efficiency for the intended application... do you need low end pulling torque, do you need top end racing speed, do you need a wide range of rpm efficiency across the board, or do you need to putter to the grocery store drivability...? One who finds that 'secret edge' for his/her application will have an advantage over all the others... Jim