What does it mean when an app says hidden on an iPhone 5?

Got on my boyfriends phone and found a folder labeled "entertainment" and when I opened that it had various apps but one just said "hidden" and it was plain gray. I didn't click on it because I figured it had some sort of passcode w it.

He has locked that app, so only he can view or use it. Many people have app lockers to keep random people from going through their phone opening settings or apps. I lock my settings, so if anyone is using my phone, they can't change anything that matters.