As for the sphere SEO, then the index usually means an ordered database search engine, filled with information about the websites analyzed by robots, the existence of which he is aware of. Sites listed in the index are periodically scanned to save updated copies of their pages in search engine cache and subsequent presentation of relevant search results by user requests.
The process of entering web resources in an index is accordingly called indexation or indexing.
To start site search promotion, you need to add it to the search engine index. This usually happens automatically: if there is at least one back link on a third-party resource that is known search robots, sooner or later they will go over it, find a new site and bring it into the index. But if you need to speed up this process, you can use "adduril»- the function“ Report on a new site ”(present in all search engines (Add URL).