Gulp is yet another tool that you will find highly useful, and a required tool in your overall toolchain for SharePoint Framework development projects. Whereas you will use npm to fetch the necessary packages and Yeoman to generate your projects, you will use Gulp to build your projects with all the necessary parameters and dependencies.
Gulp automates and allows you to enhance your build workflow. This is done with a configuration file called gulpfile.js, which allows you to add custom actions and tasks when building your project.
With .NET development, where you typically use Microsoft's Visual Studio development environment, you would typically just select the Build menu from the top toolbar, and then click on Build solution. This would compile and build your full-trust solution for SharePoint.
However, when using Gulp, you type gulp <action>, such as the package, to start packaging your code into a re-distributable and deployable package.
