Electricity (or "power") is a type of energy that is made by machines called generators. To make electricity, generators take fuel (like coal, oil, natural gas, or nuclear) and burn it to make a spinning motor inside the generator turn. This spinning motor creates a magnetic field, which is what makes electricity.
Unfortunately, burning fuel to make electricity comes at a cost to the environment. Burning fossil fuels like coal, oil, and gas creates air pollution that can harm people, plants, and animals. Burning these fuels releases harmful gases like carbon dioxide and sulfur dioxide into the air. The gases mix with water vapor and create smog (a brownish haze) or acid rain (rain with harmful acids in it). This can be damaging to plants and animals and can even cause breathing problems in humans.
Another environmental concern with electricity generation is the disposal of nuclear waste. Nuclear power plants create electricity by splitting uranium atoms, which creates a lot of heat. This heat is used to boil water and turn a turbine, which then creates electricity. Although nuclear power has become much safer in recent years, the waste products are still extremely hazardous and can be damaging to the environment if not disposed of safely.
So, in a nutshell, using fuel to generate electricity creates air pollution and burning nuclear fuel to generate electricity creates hazardous nuclear waste that is difficult to dispose of safely. Both of these things can be damaging to the environment, and that's why it's important to be aware of the environmental concerns with electricity generation.