Grunt is a JavaScript task runner.

As the website https://gruntjs.com/ says: “In one word: automation. The less work you have to do when performing repetitive tasks like minification, compilation, unit testing, linting, etc, the easier your job becomes. After you’ve configured it through a Gruntfile, a task runner can do most of that mundane work for you—and your team—with basically zero effort.”

The website goes on to say: “The Grunt ecosystem is huge and it’s growing every day. With literally hundreds of plugins to choose from, you can use Grunt to automate just about anything with a minimum of effort. If someone hasn’t already built what you need, authoring and publishing your own Grunt plugin to npm is a breeze.”