Indexing is simply the work the Search Engine Robots do to give you information on are tanning beds bad. How does an indexing robot decide what to index? Well they just send their Bots or Spiders to crawl the web looking for are tanning beds bad on web sites.

If an indexing robot finds a document that contains are tanning beds bad, it may decide to parse it, and insert it into its database. How this is done will depend on the robot. Some robots index the HTML Titles that contain are tanning beds bad and keep them in their database whilst others will look for are tanning beds bad in the first few paragraphs, or parse the entire HTML and index all words.