gulp-htmllint is a Gulp plugin that serves as an interface layer for htmllint, allowing developers to identify and report on HTML code issues within their Gulp workflow. It provides options for custom rules, configuration files, plugins, and error handling, making it a versatile tool for maintaining HTML code quality. This plugin is ideal for web developers and front-end engineers who use Gulp as their task runner and want to ensure their HTML code adheres to best practices and standards.