Sails uses Grunt for asset management. This file contains configuration information for the GRUNT tasks that Sails for this purpose.
If you created your Sails app with
sails new foo --linker, this is also where you can define the location of files that are automatically minified and injected (in order) into the views rendered by your app.
At the top part of this file, you'll find a few of the most commonly configured options, but Sails' integration with Grunt is also fully customizable. If you'd like to work with your assets differently you can change this file to do anything you like!
More information on using Grunt to work with static assets: http://gruntjs.com/configuring-tasks