What is the meaning of putting these in <a> tag?

<a href=“www.example.comrel=“no follow” target=“_blank”></a>

Anybody tell me the real use of nofollow and blank ?

“nofollow” tells search engines not to follow the link. This article gives examples of where and why you might want to use that: https://support.google.com/webmasters/answer/96569?hl=en

(If you want to exclude an entire page or directory from being indexed, you should use a robots.txt file.)

target=“_blank” forces the link to open in a new window, which has long been considered bad practice:
http://www.trilithium.com/johan/2005/03/target-blank/