Tags are used to track versions in Git. There are lightweight tags and annotated tags, you should generally use the annotated tags. These tags are created using the following command.

git tag -a v1.0 -m 'Finally made it to v1.0'

Show more information about a tag or version using the show command.

git show v1.0

List all tags using the tag. Wierdly, -l and --list are optional.

git tag
git tag -l
git tag --list

Read the documentation here