When we talk about renewable resources we are talking about resources that we can use, and then after waiting a bit they are still there. They will renew themselves. If we dig up a lump of coal and burn it, then it is not going to somehow renew itself and become new coal. But for example if we chop down a tree from the forest and burn that, then over time a new tree will grow in its place. We just need to make sure not to chop down the entire forest and destroy the ecosystems that support the tree. And no matter how many wind turbines we put up the wind is still going to blow, no matter how much water goes through a hydro power plant there is still more rain filling up the rivers, no matter how many solar panels we build the sun is still going to shine. All of these are energy from renewable resources and can in theory be used indefinitely.

Nuclear is often thrown in with the renewable energy sources even though it is technically not renewable. It is just going to take extremely long time before we have used up all of our uranium resources, and probably thorium as well. When we finally get a commercial fusion power plant it will have even more available resources but still technically not renewable.