A Gulp developer is a software professional who uses Gulp.js, a task runner tool in JavaScript, to automate routine tasks in the development process. These tasks can include compiling source code, running tests, minifying files, and refreshing browsers. The developer writes Gulp tasks in JavaScript or CoffeeScript, defining the order and conditions for each task. They also manage dependencies and ensure that tasks run efficiently and correctly. Gulp developers work closely with other developers on the team, integrating Gulp tasks into the overall development workflow. Their work helps increase productivity and streamline the development process.