I was pretty confused and intrigued by "instant deployments" as well.

If you go to their help docs, you can see that they can integrate directly with a few services (digital ocean and another that I can't remember) to "instantly deploy" your app.

We have a page showing our deployment process but It was removed recently as it's being improved.

We connect to any ssh service and run the commands to deploy your application using GIT.

This saves you from having to setup hooks.

Deployments can be automatically triggered.