gulp-tap is a Gulp plugin that allows you to tap into a stream and perform actions on each file as it passes through. It's ideal for modifying file contents, logging file paths, or performing validation without disrupting the main Gulp pipeline. Unlike other more heavyweight solutions, it provides a simple, lightweight mechanism for debugging and manipulating file streams mid-pipeline, allowing for focused and flexible handling of individual files. Useful, for example, to modify code slightly on the fly, or execute a command for each file going through the stream.