Crawling is the process when Googlebot or other Search Engine bots, looking over the code/content for each URL they find.
Indexing is the process were Search Engines Stores and Organizes the Content found during the Crawling Process.
Ranking is the process search engines use to determine where a particular piece of content should appear on a SERP.
Crawling is the discovery process in which search engines send out a team of robots (known as crawlers or spiders) to find new and updated content. Content can vary — it could be a webpage, an image, a video, a PDF, etc. — but regardless of the format, content is discovered by links.
The bot starts out by fetching a few web pages and then follows the links on those webpages to find new URLs. By hopping along this path of links, crawlers are able to find new content and add it to their index — a massive database of discovered URLs — to later be retrieved when a searcher is seeking information that the content on that URL is a good match for. – MOZ –
If your backlinks can’t be found by Search Engine bots, then there’s no way you’ll ever Rank your Moneysites in the SERPs (Search Engine Results Page).
