It works by parsing a Procfile in your project and opening a pseudoterminal for each process you specify in its own tab that you can interact with independently. If you've worked on Rails apps that use Foreman to run multiple processes, this should work as a drop-in replacement.

I got nerd sniped by Aaron Francis into building a little TUI process manager a couple of weeks ago. His project Solo (github.com/aarondfranci...) looked like a great way to run multiple processes while developing locally, but it's only for Laravel apps. So I built my own general purpose version: