There is a limited amount of fossil fuels (our main source of energy for powering our appliances and cars) on Earth. Why? What is an example of a "renewable" energy source, and why is it considered "renewable"?

There, is a limited amount of Fossil fuels because, there isn't a supply of it that will last forever/for the long term. An example, of a renewable energy source would be Solar which has a consistent and a supply that will last for awhile and wont run out any time soon. (However, it isn't the most efficient power source)