Answer:
Energy is measured in joules. And it is a derived unit. An example that you use in energy is horsepower.
On the web an easy definition: Kinetic energy is motion; it is the motion of waves, electrons, atoms, molecules, substances, and objects.
Also, everything consists of energy. For example, when you turn a page from a book, that is using energy. Or when a ball is rolling down a ramp, it is using kinetic energy. You can also have potential energy, which is the energy stored in something when it isn't moving. For example, when the ball is about to roll on the ramp, it is in its starting point with potential energy.
And finally elastic energy:
Elastic energy is the mechanical potential energy stored in the configuration of a material or physical system as it is subjected to elastic deformation by work performed upon it. Elastic energy occurs when objects are impermanently compressed, stretched or generally deformed in any manner.
For example, an elastic string. When you stretch it, it is the potential anergy stored in the string you are stretching. When you release it, it flies in the air and changes to kinetic energy.
