Resources
Some of Earth’s resources are infinite. This means that we have an unlimited supply of them because they can always be made again. Solar panels supply us with infinite, renewable energy because the Sun will shine for as long as humans exist.
Some of the resources on Earth are finite. This means that we will never be able to replace them once they have been used up. Fossil fuels are not sustainable because there is no way that they can be made again while humans are alive.