(1) Commonly used in blogs, site authors attach keyword descriptions (called tags) to identify images or text within their site as a categories or topic. Web pages and blogs with identical tags can then be linked together allowing users to search for similar or related content. If the tags are made public, online pages that act as a Web-based bookmark service are able to index them. tags can be created using words, acronyms or numbers. Tags are also called tagging, blog tagging, folksonomies (short for folks and taxonomy), or social bookmarking.

See also tag and tag cloud.

(2) The act of placing RFID labels bar codes on items is called tagging.

Micro Persuasion Blog
Tagging is powerful because consumers are creating an organizational structure for online content. Folksonomies not only enable people to file away content under tags, but more importantly also share it with others by filing it under a global taxonomy that they created.

Using Technorati Tags
Think of a tag as a simple category name. People can categorize their posts, photos, and links with any tag that makes sense.

You're It! A Blog on Tagging
Provides news and resources for the online tagging community.