My car broke. I think it's a battery issue.

grumpyolddude has it right. It Could be as simple (and cheap) as loose or dirty cables.
Clean the cables.
That's the cheapest and easiest, so do that first.
The two round pieces that stick up from the top of the battery are called terminals or posts. The heavy wires that attach to them are called cables.
Try twisting the cables around the terminal posts. If one of the cables is a little loose it won't send enough electricity to the starter to make it engage the flywheel. If the cable moves twist it back and forth while pushing down. Then tap it with something like a small hammer. Then try to start it again. Good luck.