Most of our electricity comes from power stations that use fossil fuels like coal and oil.
The power stations burn the fossil fuels to make our electricity and in that process a LOT of greenhouse gas is made, including carbon dioxide and methane. This is why they are called dirty sources of energy.
It is the greenhouse gases that are causing the Earth's atmosphere to warm, which scientists tell us will cause the climate to change. It is understood that this will cause more extreme weather, the spread of diseases and threaten the habitat of all living things.
Coal, oil and gas are non-renewable sources of energy because we can only use what is available and once they have been used up, that's it!