grunt is the build tool for the Angular.js side of things. It is doing a lot of other html front end stuff to make the SPA. Also grunt has a watch process that

grunt is the build tool for the Angular.js side of things. It is doing a lot of other html front end stuff to make the SPA. Also grunt has a watch process that see code changes, it will then compile them and have the server get the browser to reload content to get the new version. When this gets deployed to your production server, you will probably use the same server process that handles the Rails requests. grunt is for development only.