How Do You Deploy a Version in a CI CD?

I was investing in for a project which was like, how can we easily deploy and mark a version as X? How do you handle something like this in a CI CD? Because if you want to track down a bug, you want that specific version. And I've seen systems where the CI picks up when you push a tag and then they do things that so like somebody is tagging manually basically and then pushing that. This is just details on how exactly I do it for this project. So I mean, your mileage may vary, right?