Indexing is simply the work the Search Engine Robots do to give you information on national car rentals. How does an indexing robot decide what to index? Well they just send their Bots or Spiders to crawl the web looking for national car rentals on web sites.
If an indexing robot finds a document that contains national car rentals, it may decide to parse it, and insert it into its database. How this is done depends on the robot. Some robots index the HTML Titles that contain national car rentals and keep them in their database. Others will look for national car rentals in the first few paragraphs, or parse the entire HTML and index all words.
Go Meetings Resources national car rentals to discount car rentals in dallas