It's a common marketing term: http://lushdigital.com/curiosity-gap/: A Marketer’s Guide to the Curiosity Gap “You’ll never believe what this marketer accidentally published on the company blog” “We tried this shocking content marketing technique… and it worked!” Does this style of headline seem eerily familiar? That’s because they’re using a technique called the “curiosity gap” to pique your interest and persuade you to take action. The curiosity gap is frequently used by sites like Upworthy and BuzzFeed, yet some see it as an undesirable technique. Many in the content marketing space see the technique as a cheesy and manipulative way to get high click-through rates to online content. For newcomers to the term, the “curiosity gap” is the discrepancy between what we currently know and what we would like to know. Marketers can use the curiosity gap in headlines to entice readers to seek more information. Theoretical foundations The curiosity gap is based on “the information gap theory of curiosity” by academic, George Lowenstein. According to Lowenstein, curiosity is a state that occurs when people can identify a gap between what they currently know and what they would like to know. Curiosity triggered by information gaps related to a person’s competence is particularly strong and information gaps of all kinds prompt people to take action. Lowenstein came up with his information gap theory in 1994 long before the rise of social media. His theory has manifested itself in the widely popular “curiosity gap” technique used in social media and online content distribution.

'Curiosity gap' is not a phrase used in English, I think the author made it up! He is basically saying that stores are tweeting interesting stories and trusting to the natural curiosity of most people to get clicks to their sites. People naturally want to know the answer or to see what comes next, so they click through. Neal