Having played around with the Visual Studio 2015 preview a bit I've tried to learn how Gulp integrates with the Web Application project.
What does it do?
By default the project template comes with a gulpfile (shown in the image as #1). This is configured to take the dependencies from Bower (which is a package manager loading a few jQuery packages in by default) and copy them to the
wwwroot/lib folder (#3 in the image).