Eleventy is a static site generator that offers a low barrier to entry, allowing developers to quickly create and customize websites without shipping extra code. It provides features such as frontmatter for layouts, global data with the _data directory, overriding global data, grouping posts with tags, shared data for all files in a given directory, pagination built into collections, and creating pages from third-party data. Eleventy's flexibility and customization options make it an attractive option for developers looking to build fast, efficient, and scalable websites.