We run hardware, our own physical servers, in a bunch of regions around the world. We have an API (and a CLI) that will take a Docker container (or a Dockerfile, or a bunch of other things), turn it into a VM, and it run it on that hardware. That VM is given a routable Anycast IP address, so your users will automatically tend to hit the closest instances of your app.

Hope that helps!

Having a go at writing the elevator pitch myself, since I think the others I've read have been overly technical.

It's a platform as a service. It'll take your docker application (usually a web application) and run it on the internet. It'll also allow you to run it in many locations around the world transparently (using the same IP address / anycast) so that users closer to those locations will get better/lower latency.

It's a CDN for your application.

(There's more to it than this, but as far as elevator pitches go, sufficient?)

It's Uber for Heroku

the website for fly.io is extremely well written in explaining fly.io in terms of AWS

So no? I went to the site and didn't see anything nor did a google search turn up anything