Luis Von Ahn

And see, this is pretty different than many other subjects.

For example, take math.

In the case of math, just knowledge of math does not increase your income potential, because usually you have to learn math to then learn physics to then become a civil engineer.

That's how you make more money.

Whereas with languages, if you were a waiter and you learned English, now you can be a waiter at a hotel and make more money.

So we decided, well, let's get started by teaching languages.

Now, we also convinced ourselves that the only way to really reach a lot of people was by using a mobile phone, or a smartphone in particular.

See, building schools all over the world is simply too expensive.

On the other hand, most of the world's population already has access to a smartphone, and the trend is that that fraction is only going to increase.

So ...

we decided at the time that we would make a way to learn foreign languages on a mobile phone that was accessible to everyone.

And then we called it Duolingo.

In order to truly be accessible to everyone, rich and poor, Duolingo uses a freemium model to support itself.

What that means is that you can learn as much as you want without ever having to pay, but if you don't pay, you may have to see an ad at the end of a lesson.

Now, if you don't like ads, you can also pay to subscribe to turn off the ads.

And it turns out that the vast majority of the revenue for Duolingo comes from people who pay to subscribe to turn off the ads.

Now, who are these people who pay to subscribe to turn off the ads?

Well, they're usually people, well-off people, in rich countries like the US and Canada.

Who are the people who don't pay to subscribe?

They usually come from poorer countries like Brazil or Vietnam or Guatemala.