Cloaking

This is done by delivering content based on the IP addresses or the User-Agent HTTP header of the user requesting the page.

However, it can also be a functional (though antiquated) technique for informing search engines of content they would not otherwise be able to locate because it is embedded in non-textual containers, such as video or certain Adobe Flash components.

[1] Cloaking is often used as a spamdexing technique to attempt to sway search engines into giving the site a higher ranking.

[2] One use of IP delivery is to determine the requester's location, and deliver content specifically written for that country.

For instance, Google uses IP delivery for AdWords and AdSense advertising programs to target users in different geographic locations.