Passwords detected in data leak

Hi, I was checking my passwords on the password app on my phone and I’ve noticed a notification for a few saying they’ve been detected in a data leak. I tried changing them, but the websites are very old and don’t really have the option available. Should I worry? Has this happened to anyone else? I’ve requested for my accounts to be deleted but I’m very doubtful anyone is checking these requests. Some of them are also with an email that no longer exists. I’m very paranoid and freak out easily, I’m not very tech savvy and although these are not important websites I’m freaking out a bit. What does data leak actually mean?