mprocs runs multiple commands in parallel and shows output of each command separately.
When you work on a project you very often need the same list of commands to be running. For example: webpack serve, jest --watch, node src/server.js. With mprocs you can list these command in mprocs.yaml and run all of them by running mprocs. Then you can switch between outputs of running commands and interact with them.
It is similar to concurrently1 but mprocs shows output of each command separately and allows to interact with processes (you can even work in vim inside mprocs).