I have come across this dofollow and nofollow topic quite several times in many forums and I have replied to them as per my knowledge. What I know is secondary, but I want to know clearly about the topic and how far they have impact in popularizing the website.

Nofollow means that the web author uses the re="nofollow" tag to prevent bots like google from crawling a particular page. The search bots to not follow the link, meaning pr is not passed.