When you return an item to a merchant in person or online, the merchant processes your refund and sends it back to your card. The money can take up to 7 business days to appear back in your account, depending on how fast the merchant processes them.
A canceled transaction like an Uber ride or pending Amazon order usually causes an authorization hold on your card from the merchant. These generally take up to 10 business days to expire from the authorizing merchant as well.