Simple machines include: inclined planes, pulleys, levers, wheel and axle, wedge, screw
The machines are generally used to reduce the force necessary to do some amount of work. The tradeoff is that to get smaller input forces the distance must be larger. This results in the same or less work being done. Less work is done if some of the energy is lost to friction.
Important factors with machines are Ideal Mechanical Advantage (IMA), Actual Mechanical Advantage (AMA) and efficiency. These terms and their math definitions are included in the files linked in the table below.
Work = Force x displacement. W=Fs. Force and displacement are both vectors and must be in the same direction to calculate work. Work is a form of energy with metric units of Nm, Joules, kg m2/s2, and watt seconds. The connection with machines is the Law of Conservation of Energy: Energy is not created or destroyed.