Besides means in addition to something, or except for something. When your teacher says “Besides math, what's your favorite subject?”, she's asking what you like in addition to math. When you say “Besides my best friend, no one else showed up to help,” you mean except for that one person.

The word helps you add information or make exceptions. If someone asks whether you're ready for the test, you might say “I know everything besides the last chapter,” meaning you know all of it except that one part. Or if you're listing reasons to visit the museum, you could say “Besides the dinosaur exhibit, they also have amazing gems and minerals.”

People sometimes confuse besides with beside, which means next to. Remember: beside (without the s) means physically next to something, like sitting beside your friend. Besides (with the s) means in addition to or except for. If you say “Besides me, who's coming?”, you're asking who else is coming. If you say “Beside me, there's an empty seat,” you're describing the physical location next to you.