Facebook just spent $16 billion to acquire a service that … most Americans have never heard of.

Yes, this could be a sign of the ever-accelerating pace of our technological zeitgeist/start-up development/cultural ruin. But in actuality, WhatsApp isn’t obscure at all — it’s just more popular abroad, which is why many Americans aren’t familiar with it. (And why, in all likelihood, Facebook wanted to buy it.)

It’s worth a download, though, and not just because it’s free for the first year. WhatsApp is basically an instant messaging service — you can send text, picture and video messages to anyone with the app, set away statuses similar to Gchat or AIM, and organize contacts into groups for easy mass-messaging. The concept is simple, but it’s really caught on. WhatsApp currently has 450 million users, many of them in the U.K. and Asia, where it competes with other messaging apps like WeChat.

It’s ironic — or perhaps illuminating — that WhatsApp has historically been poised as a kind of competitor to Facebook: “Teenagers say goodbye to Facebook and hello to messenger apps,” read a November headline in the Guardian, which credited superior privacy settings and the absence of killjoy parents as reasons the service was popular among young people. WhatsApp, unlike Facebook, neither serves ads to its users nor collects data from them.

There’s obviously no way to know, at this very early stage, what kind of impact the Facebook acquisition could have on that front. In a message on Tumblr, at least, WhatsApp’s founders promised not to “compromise on their principles.” Then again, $16 billion buys a lot!