One use of this word refers to the urban sport of spray-painting things. Your typical tagger will be a guy dressed in threadbare clothes with a little brown glove and a can of spray-paint or a Magnum paint marker. Taggers sometimes belong to gangs of taggers who all add their little symbol to their graffiti. They comprise a subculture with its own set of rules and requirements. Graffiti art might be hard to read, or look a little schizo, but a little bit of practice and you will be able to recognize and read it.

In SGML terminology, tagging is merely a process of 'marking' by putting pair of pair of angled brackets around that which is tagged. One pair consists of one opening and one closing angled bracket and of such there are two pairs. The second pair however has a slash in it as well, the one that immediately follows the opening angled bracket.

Tagging is a way of marking something (a photograph, a wiki entry, an idea) as belonging to a category. For example, on Flickr, a photo sharing website, you can tag both your own and other people's photographs. And on Tagberry, the entire content of the website is made up of tags. Tagging is a way of using hyperlinks to show how things interrelate, and as such, it is extremely subjective.