heroku is (was?) a platform for hosting web apps with a lot of nice ergonomics, to let you run commands like "heroku up" to get your app running on the web with minimal fuss.
this appears to be a project to give you the niceities of a PAAS, without actually providing the platform.
Heroku is still good for tons of stuff. After Salesforce bought it, it stopped getting much better, they removed part of free quota, some add-ons disappeared, and the like. For example, http2 support just went beta on may. It's a shame.
this appears to be a project to give you the niceities of a PAAS, without actually providing the platform.