1. Get links from related popular pages on the internet. 2. Setup Google Webmaster Tools and Sitemaps. 3. Get a domain that is already indexed and have it 301 to your website. (only if you don't use the redirected domain anymore)
"Crawler" is a generic term for any program(such as a robot or spider) used to automatically discover and scan websites by following simply its just a Googlebot.
getting connection through multiple links from other sites on the web is important for indexing of a website.