Git, tags are used to typically to indicate important milestones such as

releases 

or

version 

numbers. Lightweight tags:

git tag v1.0.0 // tags for previous commits (refers to the last commit)
git tag v1.0.0 <commit-hash> // tag for specific commit

Annotated tags:

git tag -a v1.0.0 -m "Version 1.0.0 release"

checkout to tag:

git checkout v1.0.0
git checkout master // to return the last commits again

Listing all tags:

git tag

Deleting a tag: // deletes only tag - not commits

git tag -d v1.0.0

Create a tag for a branch:

git tag v1.0.0 master

push tag to a remote repository

 git push origin v1.0.0