Crawling is just to visit a site by search engines. But Indexing is to "add" or "include" the page is search engines.
Crawling is just to check the website for pages and inner pages... and indexing is after crawling index those pages.
These two terms are interrelated. Search engines perform both these processes. Crawling is the method performed by the SE in requesting a URL. Indexing, meanwhile is the product of successful crawling.
Search engines crawls for the website and indexes the webpage of the site if it is good .It crawls to index the site.
Crawling ----- Search Engine Visiting to our web pages Indexing------ our Web pages are added in search engine database
Crawling - the process of confirming whether pages exists or not. Indexing - confirmed urls that inclueded in search engines.
Crawling means searching for web pages. Indexing means adding those crawled pages into possible search results.