Religion and mythology are two subjects that talk about gods and beliefs, which people used a long time ago to explain things they didn't understand.
Religion is like a big rulebook of how to act and behave to please a god. You might go to a big building called a church to pray and hear stories about the god they worship. People follow religion because they believe it will make their life better and happier.
Mythology is kind of like storytelling. It tells stories about gods and goddesses who have special powers and do amazing things. It's not necessarily meant to be followed like religion, but it's still important because it tells us about the cultures and traditions of people in the past. You might read a book about mythology and learn about how people thought the world was made, or why there are seasons.
In short, while religion tells you how to behave to please a god, mythology tells you stories about what gods are like and what they can do.