Facebook tagging is a way that you can notify friends that you've updated something on Facebook with their name or picture on it. When Facebook first introduced tagging, users could only tag one photo at a time, making it time-consuming to tag friends when uploading large quantities of photos. You can now, however, tag entire albums in Facebook.
About Facebook Tagging
Tagging is a way to identify individuals in photos, comments or status updates posted on Facebook. When you tag someone, Facebook sends a notification to those friends, letting them know that you've tagged them. You can tag up to 50 people in a single photo and up to 10 people in a single comment. Additionally, users can control the privacy options for tagged photos, controlling who can and can not see tagged photos, and can remove tags of themselves on photos to protect their privacy.
Tagging Individual Photos
When you upload a photo, you can individually tag people in the picture by selecting the "Tag This Photo" option in the bottom left corner of the photo. Facebook then gives you an option to click on individuals in the photo and type in their names. This allows other users who view the pictures to hover over the tags below the photo and see which tags belong to which individuals in the photo.
Tagging Entire Albums
Facebook also offers the ability to tag entire photo albums. When you upload large groups of photos, Facebook automatically groups photos together based on the recognized friends and suggests tags for the photos. You can then either approve or cancel the tags and Facebook will automatically apply them. Additionally, you can select the "Tag Photos" button in the upper right corner of a photo album, type in the name of a friend and click on each image that contains that friend to tag that friend in several pictures in an album. Repeat this for each friend that you want to tag in that album.
Tagging Friends in Comments
Another way that you can tag friends is to comment on the photo or album and tag them in the comment. You can tag a friend in a comment by typing the "@" character, then typing in the friend's name. A drop-down menu will appear listing all friends that match the letters you've typed out so far. Click on the name of the friend to apply the tag to the comment.