Proxies HTTP requests from a temporary server with a public domain record to a localhost server. Useful for some development environments, and also if you don't feel like dealing with networking in docker. At one company I worked at, we ran everything through vagrant and running ngrok was easier than a junior java engineer learning anything about networking.
It's like they can do almost anything...what exactly? .... well whatever you can think of.....er like what?
You can open localhost to the internet.......?????????? Sorry?
Anyhow if anyone would care to put me out of my misery by explaining a bit I'd be grateful.