The Internet Archive has capitalized on the popular use of the term "WABAC Machine (WABAC machine)" from a segment of the old Rocky and Bullwinkle (Rocky and Bullwinkle Show) cartoon, and uses the name "Wayback Machine" for its service that allows archives of the World Wide Web to be searched and accessed.
This service allows users to view archived web pages. The Wayback Machine was created as a joint effort between Alexa Internet and the Internet Archive when a three-dimensional index was built to allow for the browsing of archived web content - faq
Millions of web sites and their associated data (images, source code, documents, etc.) are saved in a database. The service can be used to see what previous versions of web sites used to look like, to grab original source code from web sites that may no longer be directly available, or to visit web sites that no longer even exist.
Not all web sites are available because many web site owners choose to exclude their sites. As with all sites based on data from web crawlers, the Internet Archive misses large areas of the web for a variety of other reasons. A 2004 paper found international biases in the coverage, but deemed them "not intentional" - scit.wlv.ac.uk