Crawling and Indexing in the SEO industry

Most people get confused with Crawling and indexing. Somehow they mixed up with those two terms.

Gooogle Crawling
When you allow the Google bot to look and analyse all the contents or codes of your pages . But you can refrain Google from Crawling if you block your page via robots.txt. Therefore Googlebot wont be able see the page but it allows your page to show the others. Therefore potential ranking will be lessened than expected.


Google Indexing
Indexing means once your page iseligible to show in Search result. But noindex meta robot tags refrain your page to show up in SERP.

An example can make it easy to describe this two terms.
You allowed to your friend (Googlebot) to look around your room(page) and make a comment if everything(content/code) is ok or there might need some changes. Which means Crawling. Your friend is also allowed to show to others (SERP). Which means Indexing. Your friend might be blocked  to enter the room but he can point out the others (Index) to enter the Room, even if there is a clear direction not to let anyone to visit your room because he doesn't know what is inside.

If you are allowed to your friend to check your room and let him know not to show (with noindex meat robot tag), your friend will check but not let anyone to visit your room.