What are Github Tags ?
Tags are associated with commits, so you can use a tag to mark an individual point in your repository's history, including a version number for a release.
How to create Tags ?
Step 1
You should have a repository, if you don't go on this page to know how to create a repository.
Step 2
Navigate to the repository and click on tags
Step 3
Click on Create a new release 
Step 4
Click on Choose a tag to choose a tag and target: to choose the branch you are targetting.
Step 5
Add a title and a description about the tag.
Step 6
You can choose if it's a pre-release(non-production ready) 
You can publish it or save it as a draft.