Every Blogger wants their new posts to be crawled and indexed by Google but it's not as easy as you think. There's no guarantee if Google will even crawl them or not.
Google Webmaster is a tool that gives us the chance to Submit your website/blog sitemap to Google so our blog can be easily and rapidly indexed in Google search engine. Once you have been able to submit your website sitemap, What Google does is to start sending bots to your website or blog and crawling your website or blog pages and posts.