Hyde is a pluggable content generation system, with focus on generating Drupal content to HTML pages. The name comes from a popular similar system, Jekyll.
Why?
The time when a browser was just a dumb client and servers had to do all the heavy lifting when it comes to business logic is over. Modern browsers today aims to be application platforms onto which you can run your code, and there are some pretty impressive demonstrations of this in many places today.
Drupal and systems like it are currently operating the old school way: The system handles everything, content administration, the actual rendering of the content, and any other interactive functionality that goes on around it. This is a complicated system, and it relies on several pieces of software to deliver content to a user: We have to have at least a web server, some middle-layer application and a database involved in every request.