What is the difference between Indexing & Crawling?

Indexing:
Having your page Indexed by Google is the next step after it gets crawled. By no means does every site that gets crawled get indexed, but every site indexed had to be crawled.  If Google deems your new page worthy, it will index it
Crawling:
Crawling or spidering is a term used when Google, or another search engine, sends its bot to a web page or web post and "reads" the page.  Don't let this be confused with having that page being indexed.  Crawling is the first part of having a search engine recognize your page and show it in search results.

Crawling means the visit of Google to track your web page. This process is done by Spider of Google crawler.
Indexing means when crawling has been done putting the results on Google's index .

Crawling or spidering is a term used when Google, or another search engine, sends its bot to a web page or web post and "reads" the page.  Crawling is the first part of having a search engine recognize your page and show it in search results.

Having your page Indexed by Google is the next step after it gets crawled. By no means does every site that gets crawled get indexed, but every site indexed had to be crawled

Crawling is the process or reading through your webpage source by search engine spiders. They provide a cache certificate after a successful crawl. Indexing is updating the cached webpages in search engine database. Indexed webpages are now ready for search engine rankings.

Crawling is the process of an engine requesting — and successfully downloading — a unique URL. Obstacles to crawling include no links to a URL, server downtime, robots exclusion, or using links (such as some JavaScript links) from which bots cannot find a valid URL.
Indexing is the result of successful crawling. I consider a URL to be indexed (by Google) when an info: or cache: query produces a result, signifying the URL's presence in the Google index. Obstacles to indexing can include duplication (the engine might decide to index only one version of content for which it finds many nearly identical URLs), unreliable server delivery (the engine may decide to not index a page that it can access during only one-third of its attempts), and so on."

Indexing is updating the cached webpages in search engine database. Indexed webpages are now ready for search engine rankings.
When Google visits your website for tracking purposes. This process is done by Google's crawler.This is a process execute by search engine crawler when searching for relevant websites on the internet.