a.k.a. social bookmarking, social tagging, tags

Tagging identifies someone in a post, photo or status update that you share on Facebook, or other social networking sites. It can also refer to tagging yourself on a location-based service to broadcast when you've arrived somewhere.

Originally tagging was a grassroots phenomenon whereby users label websites with descriptive tags, building a network of knowledge dubbed folksonomy, a term deriving from a taxonomy of knowledge organized by ordinary folk.

The term "tag" has also evolved to refer to content that identifies a particular image or file, to be used in conjunction with other images or files of the same tag. Now known as a hashtag on social media sites, it's what "like-minded" communities form around, specific hashtags, such as #IceBucketChallenge. When you search that particular hashtag on the social networking site, you'll see all the posts and users related to that tag or topic.

NetLingo Classification: Online Jargon