At this point, you’ve likely heard the buzz surrounding the social media app, WhatsApp, possibly the next big thing in social media interactions. Just purchased by the Facebook crew for a whopping $19 billion, it’s still largely under the radar in the U.S. But, if Mark Zuckerberg’s giddiness over the purchase can be any indicator, it may become as much a part of our social mediascape as Twitter.

So what is it, exactly? Essentially, smartphone users can download this app and access texting capabilities for free, sending voice, text and picture messages without the cost of a typical SMS—the app pulls into your pre-existing data plan instead.

The brilliant difference between this and already existing services is that it can be used across multiple user platforms—so for instance, an iPhone user could send a group chat to a Blackberry user and an Android user for free.

Though spending $19 billion for a service that users download for free raised a lot of eyebrows, this could potentially expand Facebook’s reach exponentially—the service currently has 470 million users.

Click here to read about WhatsApp co-founder Jan Koum’s journey from food stamps to billionaire status.