Energy comes in different forms: radiant (light), thermal (heat), kinetic (motion), chemical, gravitational, nuclear and electrical, etc...
Energy must be generated in some way (by burning coal, by a nuclear reaction etc.)
For example, when we switch on the light in our home the electrical power (energy/seconds) is manufactured from an electrical generator and then delivered to our home.
We are concerned with nonrenewable sources where we get most of our energy. We are using them up and they can’t be replenished.
Nonrenewable energy sources are oil, natural gas, coal and uranium.
Renewable energy sources are the Sun (solar energy), the wind, the Earth (geothermal energy), biomass from plants (firewood) and hydropower.