The rel=”nofollow” tag is a HTML attribute to instruct search engines not to assign any value for the given link. It is generally used in forums and websites where the web master does not want to provide link value to its members. Especially in cases where the links were posted through some automated bots to gain higher rankings in SERPs.
Nofollow tag helps to avoid the tricks and clearly informs spiders with a sign “DO NOT INDEX THIS LINK”. Links with Nofollow tag will not be counted as a backlink.
As a web master you can instruct NOT to crawl any one page or the whole directory 
using the robots.txt file. For example:
Disallow: /pagename.html
Disallow: /foldername/
hello,
When submitting to forums or directories who tag their links with “nofollow” attribute will help to promote website link popularity. Please explain about this process…