Comment by moduspol

A transaction can have multiple inputs and outputs, and with these Bitcoin wallets, they always do. Pretty much any transaction you make is going to look like it's going to at least two places: the actual intended recipient for the amount you wanted to send, and another (probably new) address that you control. The inputs could be from a single one of your addresses or multiple.

Yes, it does result in larger transaction sizes, and transaction sizes are used to calculate fees. In practice, my understanding is that the relative increase in size is not a big deal, but again, this is how pretty much all of them work.