When used as a noun, index refers to all of the web pages that Google has crawled and stored to be shown to Google searchers (e.g.: “The Google index has billions of websites”). When used as a verb, it refers to the act of Google copying a web page into their system (e.g.: “Google indexed my website today, so it will start appearing in their search results”).
Source: HSMAI CHDM Study Guide« Back to Glossary Index