Okay, so you know how there are good guys and bad guys in stories? Well, baal is a kind of bad guy called a demon.
A demon is a creature that some people believe exists, and they think demons are very powerful and can do things like hurt people or make bad things happen.
Baal is a specific demon that comes from a long time ago when people believed in lots of different gods and goddesses. Baal was one of those gods, but people started to think of him as a bad guy instead.
Some people still believe in demons like baal, but others do not. It's important to remember that just because some people believe in something doesn't mean it's true for everyone.