Popular with U.S. teenagers and in a growing number of other countries, Sarahah is obviously not the first mobile app to catch fire after quickly gaining widespread popularity among young users (remember similar anonymous apps like Yik Yak, Secret, and After School?). But, considering how sudden Sarahah’s App Store ascent has been, Fortune thought it would be helpful to put together a handy guide for any (older) readers who may be wondering what all the fuss is about.

What is Sarahah?

“Sarahah” is the Arabic word for candor or openness, and those are certainly qualities that could be used to describe the many users who are flocking to download a social app that lets them send anonymous messages. Introduced last year by Saudi Arabian developer Zain al-Abidin Tawfiq, Sarahah began as a website intended for employees to give anonymous, honest feedback to their employers. After some success in Arabic-speaking countries, Tawfiq rolled out an English version last month. Like many anonymous messaging apps before it, the new app has caught on rapidly with teens.

How does it work?

The Sarahah website describes the app pretty simply: “Sarahah helps you in discovering your strengths and areas for improvement by receiving honest feedback from your employees and your friends in a private manner.”

The app allows users to search for others who they may know and then send them anonymous messages. True to Sarahah’s origins as a tool for honest employee feedback, the app encourages users to craft “a constructive message” after they select a recipient. Users can apply filters exert some control over who sends them messages, and they can “favorite” the messages that they like—but the app does not allow them to respond to messages. Sarahah’s website notes that the app will not disclose users’ identities without consent.

How do I get it?

Users can download Sarahah to mobile devices using the iOS or Android operating systems. You can also sign up for an account on the Sarahah website to check messages.

What are people saying about it?

Sarahah developer Tawfiq told tech news site Mashable that his app is meant to promote honesty and frank expressions of feelings that transcend certain social restrictions. “There are barriers like age, sometimes it’s the position, you can’t go to someone who is a grandfather and tell them everything you think about them,” he said. “Breaking these barriers, that’s what everybody wanted.”

However, as has been the case with controversial anonymous messaging apps in the past, the fact that users don’t fear any consequences for the messages they send on Sarahah raises concerns about the potential cyberbullying and other abuse. There have already been several reports of widespread bullying on the service, with some users even complaining in app store reviews of the app about instances of racist messages and other harassment. New York magazine spoke to several Sarahah users, most of whom said they’d seen a mix of positive and negative messages on the app. “The messages are usually either really nice or really mean,” one user told the publication.

How do I connect Sarahah to my Snapchat account?

Teens have been posting links to their Sarahah profiles in Instagram to encourage other users to send them anonymous feedback. But, as Fortune reported earlier this week, Sarahah users are also using a new linking feature that the popular messaging app Snapchat added in early-July to share posts between the two apps. When Snapchat users share a new snap, they now have the option of tapping a paper clip icon that lets them paste links, which means they can simply embed a link to their Sarahah profiles into a snap to encourage their Snapchat followers to send them anonymous messages.

Is Sarahah the next big social network?

Good question. The app is catching on with an influential user group, which is good news. Other buzzy mobile apps have been able to turn popularity with young users into large funding opportunities and somewhat longer-term success. Snapchat parent Snap Inc. went public earlier this year in a high-profile initial public offering, but the company’s user growth has slowed in recent quarters and there are serious doubts about the service’s ability to compete with larger, more established social media rivals like Facebook. After all, popularity with teens isn’t a guarantee of long-term viability. Just ask fellow anonymous messaging apps like Yik Yak and Secret, both of which quickly fizzled out, while another, called Whisper, just laid off 20% of its staff.