Gulp is a JavaScript task runner that automates repetitive tasks in web development, such as minifying files, compiling Sass, and optimizing images. It uses a code-over-configuration approach, allowing developers to write tasks in JavaScript, making it flexible and easy to customize. Gulp operates on a streaming build system, which means it processes files in memory rather than writing intermediate files to disk. This results in faster build times and improved performance. It is widely used in conjunction with other tools and frameworks, enhancing the efficiency of the development workflow.