What is the deference between reactive power and power factor?

Note that this is an engineering convention, not a concept from pure physics. When you multiply voltage by current, the total "power" in volt*amps can be a combination of two types of "power". 1. active power = V*I*cos(theta) and 2. reactive power = V*I*sin(theta) where (theta) is the phase angle between the voltage and current. A physicist would say that V*I*sin(theta) is NOT power since it is performing zero work.