It's called change.

Imagine that each transaction you receive to your address is like a piece of paper money, like a dollar bill. When you want to spend part of that money, you need to receive change to only spend part of it. For example, I pay for a $15 item with a $20 and receive $5 in change.

The same thing happens in Bitcoin because you can only fully spend from an output; you cannot partially spend it. Whatever is leftover, i.e. the change, has to be sent back to your wallet, so the transaction has a change output. Most wallets will generate a new address for your change outputs, so this is what you are seeing.