What is Tag ?
Tag is (noun) 1. a label or a piece of paper or plastic attached to something to show e.g. a price, contents, or someone’s name and address 2. a children’s game where the first child has to try to touch another one who then chases the others in turn They were playing tag in the school playground. (verb) 1. to attach a label to something These coats need to be tagged before you put them on the racks. We tag birds so that we can study their migration routes. 2. to tag along behind someone to follow close behind someone (informal.) Whenever we go out for a walk my sister insists on tagging along.
source: Easier English, Student Dictionary Upper Intermediate Level