The git tag command with no argument will list the visible tags:

    $ git tag
    release-1.0
    release-1.0beta
    release-1.1

You can create a tag on your current checkout by adding a tag name:

    $ git tag ReleaseCandidate-1

You can add a tag to a previous commit by appending an SHA-1 identifier to the git tag command:

    $ git log --pretty=oneline
    72f76f89601e25a2bf5bce59551be4475ae78972 Initial checkin
    fecef725fe47a34ab8b4488a38db446c6d664f3e Added menu GUI
    ad606b8306d22f1175439e08d927419c73f4eaa9 Added menu functions
    773fa3a914615556d172163bbda74ef832651ed5 Initial action buttons


    $ git tag menuComplete ad606b

The -a option will attach annotation to a tag:

    $ git tag -a tagWithExplanation
    # git opens your editor to create the annotation

You can define the message on the command line with the -m option:

    $ git tag -a tagWithShortMessage -m "A short description"

The message will be displayed when you use the git show command:

    $ git show tagWithShortMessage

    tag tagWithShortmessage
    Tagger: Clif Flynt <clif@cflynt.com>
    Date:   Fri Dec 23 09:58:19 2016 -0500

    A short description
    ...

The -d option will delete a tag:

    $ git tag
    tag1
    tag2
    tag3  
    $ git tag -d tag2
    $ git tag
    tag2
    tag3F