Something that’s possible is something that can happen, something that can be done, or something capable of existing.
You can use possible to talk about anything that might happen. If you work really hard for a test, and you show you know the material, it’s possible that you’ll get an A. For a really hard problem like inventing a car that doesn’t use gas, you’ll need to pursue many possible solutions. If you write science fiction, you like to imagine possible worlds. Anything is possible, if you just put your mind to it!