Energy and Energy Sources

Forms of energy
1) Potential energy
Potential energy is defined as the work done against a given force (= work of given force with minus sign) in changing the position of an object with respect to a reference position (often taken to be infinite separation).
Gravitational potential energy
The gravitational force near the Earth's surface varies very little with the height, h, and is equal to the mass, m, multiplied by the gravitational acceleration, g = 9.81 m/s^2

Elastic potential energy
Elastic potential energy is defined as a work needed to compress (or expand) a spring. The force, F, in a spring or any other system which obeys Hooke's law is proportional to the extension or compression, x. F = - kx
2) Kinetic energy
Kinetic energy, T or K, is the work required to accelerate an object to a given speed.
3) Thermal energy
Thermal energy is the internal energy of matter.
4) Electrical energy
The electric potential energy of given configuration of charges is defined as the work which must be done against the Coulomb force to rearrange charges from infinite separation to this configuration (or the work done by the Coulomb force separating the charges from this configuration to infinity).
5) Chemical energy
Chemical energy is the energy due to associations of atoms in molecules and various other kinds of aggregrates of matter. It may be defined as a work done by electric forces during re-arrangement of electric charges, electrons and protons, in the process of aggregration. If the chemical energy of a system decreases during a chemical reaction, it is transferred to the surroundings in some form of energy (often heat); on the other hand if the chemical energy of a system increases as a result of a chemical reaction - it is by converting another form of energy from the surroundings.
6) Nuclear energy
Nuclear potential energy, along with electric potential energy, provides the energy released from nuclear fission and nuclear fusion processes. The result of both these processes are nuclei in which strong nuclear forces bind nuclear particles more strongly and closely. Weak nuclear forces (different from strong forces) provide the potential energy for certain kinds of radioactive decay, such as beta decay. The energy released in nuclear processes is so large that the relativistic change in mass (after the energy has been removed) can be as much as several parts per thousand.
Sources of energy
1. Bioenergy
2. Fossil Fuels (eg. oil, coal, natural gas etc)
3. Electric power
4. Nuclear (fission and fusion)
5. Geothermal
6. Hydropower
7. Hydrogen
8. Solar
9. Wind (e.g. wind, waves etc)
I hope this can help with your understanding. =)