What is Indexing in SEO and how it works?

Indexing is updating the cached webpages in search engine database. Indexed webpages are now ready for search engine rankings.

Indexing is the 2nd work of Search Engine and it done by Indexers.  Indexing's actual meaning is to give a ubique number to a file or a document and store in database.

The most important term in SEO is indexing of the web pages. Indexing is the most important activity to get the website ranked in the search engine; a website cannot get ranked until and unless it will be indexed by crawlers. So, indexing means search engines getting or collecting web pages and store in its database.

Indexing is the google crawl pages for improving ranking of the dedicated keywords.

Indexing is the most important activity to get the website ranked in the search engine; a website cannot get ranked until and unless it will be indexed by crawlers. So, indexing means search engines getting or collecting web pages and store in its database.