How Google Indexes our site
 

A "bot" is a piece of software from a search engine that is built to go through every page of your site, categorize it, and place it into a database.
Google has three well known bots: The Adsense bot, the Freshbot and the DeepCrawl.
The Adsense bot is used for publishers who have Adsense on their sites. As soon as a new page is created, the JavaScript within the Adsense code sends a message to the Adsense bot, and it will come within 15 minutes to index the page so that it can serve up the most relevant ads.

The Freshbot crawls the most popular pages on our website. Sites like Amazon.com and CNN.com have pages that are crawled every ten minutes, since Google has learned that those pages have that amount of frequent changes. A typical site should expect to have a freshbot visit every 1 to 14 days, depending on how popular those pages are.Freshbot visit is that it finds all of the deeper links in your site. It places those links into a database so that when the DeepCrawl occurs, it has a reference.Once a month, the DeepCrawl bot visits your site and goes over all the links found by the Freshbot. This is the reason why it can take up to a month for your entire site to be indexed in Google - even with the addition of a Google Sitemap.

Thanks for this info :)

Thanks for providing us such a valuable information on google crawlers.