Tag

1. A command inserted into a document or file that specifies how a document or file should look when viewed. For example, HTML tags enable a user to format text using tags, <b>bold text</b> would make "bold text".
2. A tag is a short (almost always one word) description of a HTML object or link. These tags are then placed into tag clouds also known as a weighted lists that display the most popular types of tags and allows users to find information relating to a tag more easily. A great example of a site that takes full advantage of tags is del.icio.us.
3. A tag is a type of memory that acts as a type of index for L2 (Level 2) cache.

Also see: Cache, HTML, Keyword, Memory definitions, Meta tags, XML