Humans make electricity by burning fossil fuels, using nuclear fission and harnessing renewable resources. Each method of making electricity has its own advantages and drawbacks, and humans currently use a combination of all three to generate the power people need for their everyday lives.
Fossil fuels include coal, oil and natural gas. Humans use fossil fuels to generate power by burning them, using the resulting heat to boil water and using the steam this process generates to turn large turbines. When these turbines spin, large coils of wire and the magnets inside of them generate large amounts of electricity. Fossil fuels have extremely high energy density, meaning that a small amount of fossil fuel contains a tremendous amount of potential energy. However, fossil fuels are a finite resource, and burning them harms the environment.
Nuclear fission occurs when neutrons collide with large atoms, splitting them apart and releasing enormous amounts of energy in the process. Heat generated by the fission process boils water which turns turbines in much the same process found in fossil fuel plants. Nuclear fission provides large amounts of energy, but it generates highly dangerous waste.
Renewable energy harnesses the power of the sun, tides, wind and Earth's internal heat to generate electricity. Using these resources causes little or no harm to the planet, but they generate far smaller amounts of power than fossil fuels or nuclear fission.