"Click bait" is a term for a link on a web site that is meant to lure people into clicking it by seeming more relevant or interesting than it is.
Deception and misdirection on the World Wide Web is hardly a new thing, and the process of hiding or disguising links for either commercial purposes or just for trolling is hardly new. But in its modern use, "click bait" refers to a news article of some sort that is meant to appear appealing and interesting. As with many things on the internet, "click bait" is often spread through social networking sites.
One of the secrets of click bait is to use vague terms to raise people's interest. "Find out why this young starlet has chosen to live a new lifestyle" might be about an actress who has gone on a gluten-free diet. By using vague terms, people's interest is piqued that the article might be more interesting than it is. In addition, finding out the real names behind the vague terms becomes an itch that needs to be scratched.
Click bait is one of those things that will always be around in one form or another on the internet. But it is a self-limiting condition: after seeing so many links that promise revelations and intrigue, and then being redirected to a site that is 80% advertising, banners and clunky slow-loading videos with the kernel of interest being regurgitated gossip, most internet users are weary to click bait. And the proliferation of such things on social networking sites makes those sites themselves less interesting to their users, eventually.