Definition:
A tag is a keyword used to describe an article or website. Tags are often used in social bookmarking, social news and blog entries to help users search for relevant content.
For example, a blog entry on the Green Bay Packers might be given the tags of "blog" , "Green Bay" , "Packers" , and "football".
Tag can also be used as a verb, as in tagging a blog entry or searching for articles tagged with "sports".
A tag cloud is a box containing a list of tags with the most prominent or popular tags receiving a darker and bigger font than less popular tags.