Tags should be added to the properties of a Post to aid in Searching and display.
Tags are like keywords. They are listed under:
My Site–Manage–Settings–Writing–Tags, and all the Posts with that Tag are listed separately. Tags can be used to create Topics.
OCA uses 500 Tags.
As a new Tag is typed, a drop-down list is displayed which matches your text.
Select a Tag from the list, or create a new one as you need to.