Renewable energy sources are ones which don't run out - which can be renewed. We can keep using them and using them, and we'll never run out. Examples of renewable sources include wind, water power (hydroelectric), and solar power (light from the sun).
Non-renewable energy sources are ones which do run out. As we use them to generate energy, they get used up, and can't be used a second time. There are three main non-renewable energy sources, which are fast running out: coal, oil and natural gas.

Fossils fuel is both a renewable resource and a no renewable resource. Fossil fuels like coal are made of dead animals that get compressed into coal and will be over time renewable.