k is the spring constant which is unique for every springEnergy Equations
Energy stored in elastic (compression or stretch) k is the spring constant which is unique for every spring
Energy stored in a gravational field 
m is mass in kg, g is 9.8N/kg for Earth, h is height in m
Energy stored in movement 
The unit for Energy is the Joule (J) pronounced jewel. This is equal to a Newton-meter (Nm). A joule means the energy that has to be transferred to move something 1 meter with 1 Newton of force.
Energy transferred into or out of a system is Work and is defined as the amount of force applied over a certain distance. The units for work is also joules since Work is Energy -- W=Fx
Power is how much energy is transferred in one second. The unit for power is the watt (W). A watt is how many joules are transferred in 1 second. -- P=ΔE/Δt