What is jekyll?

Jekyll is a simple, blog-aware, static site generator for personal, project, or organization sites. Written in Ruby by Tom Preston-Werner, GitHub’s co-founder, it is distributed under an open source license.
Instead of using databases, Jekyll takes the content, renders Markdown or Textile and Liquid templates, and produces a complete, static website ready to be served by Apache HTTP Server, Nginx or another web server. Jekyll is the engine behind GitHub Pages, a GitHub feature that allows users to host websites based on their GitHub repositories for no additional cost.