Jekyll is a static site generator that allows users to build static websites from dynamic content using templates, Markdown files, YAML configuration files and other features. It converts the content and templates into plain HTML files that can be hosted on any web server. Jekyll sites are fast, secure and can support plugins, themes and other functionality. To use Jekyll, the Ruby programming language needs to be installed along with the Jekyll gem, then content and templates can be organized into directories and files and converted into static HTML files via Jekyll commands.