Here I don't write theory about git tag, but I want to show minimum commands what you need for this.

Create tag

this command create new tag v2.1.0 with message

git tag -a v2.1.0 -m "xyz feature is released in this tag."

or you can use sort command (without message)

git tag v2.1.0

but this command create tag only in local repository.

Publish tags to remote repository

If I want to publish tag(s) on remote repository, then I have to push tag(s) I use only one command a this command is pushing all new tags from my local repository to remote.

git push --tags

List of tags

Last thing is display list of all tags

git tag

So this is all how to easily create tags.