A tag links a person, page, or place to something you post, like a status update or a photo. For ex...
A tag links a person, page, or place to something you post, like a status update or a photo. For example, you can tag a photo to say who’s in the photo or post a status update and say who you’re with. Tagging people, pages and places in your posts lets others know more about who you’re with, what’s on your mind and where you are.
When
you tag someone, they'll be notified. Also, if you or a friend tags someone in your post and it's set to Friends or more, the post is visible to the audience you selected plus friends of the tagged person.
When
someone adds a tag of you to a post, your friends may see what you’re tagged in on Facebook. The tagged post also goes on your profile (timeline). If you’d like, you can
turn on Profile (Timeline) Review to review and approve each tagged post before it goes on your profile (timeline) or exclude some people from seeing tagged posts of you on your Wall (timeline).
To learn more, check out our guide to tagging.