Search engine bots crawl the World Wide Web to index new content and make it accessible to searchers.
Crawling involves going through various websites or web pages on the internet and gathering the information. Indexing involves processing of that gathered information to appear on search engines.
Crawling refers to the ability of search engine to traverse to different web pages on world wide web. It is done by the web crawler also known as web spider. There are different web crawlers like google bot, bing bot, yahoo slurp etc.. Indexing is systematic arrangement of data in giant database of later retrieval.
Crawling is when a search engine essentially scans your website. Indexing is when a search engine decideds your website is good enough to be held within its index for users to find it via searches.
Crawling means the search engine optimization robot crawl or fetch the web pages while Indexing means search engine optimization robot crawl the web pages, saved the information and it appear in the search engine optimization.
In most simple words, crawling means to search & read by google bots and indexing is to arrange properly the searched data to be displayed as the result when searched by user.