Gantry is a comprehensive set of building blocks to enable the rapid development and realization of a design into a flexible and powerful web platform theme.

Gantry was born when the RocketTheme development team wanted to consolidate our extensive set of custom Wordpress theme functionality into a simple, easy to use framework. However, they wanted to ensure they didn't lock themselves into a rigid framework that would stifle the creativity and bleeding-edge design features that they had become known for. It had to be powerful enough to do everything our themes already handled, but allow them to easily extend and build-on these features with a minimum of effort and complexity.

They wanted to have a solid base we could build on top of when creating a new Wordpress theme. Anything that was common to all themes was a prime candidate to be put in the core of Gantry, and anything specific to the theme design itself should be part of the theme itself. Traditionally the Wordpress layout options are limited, but Gantry was built to provide a new layer on top of this traditional widget configuration to give an unprecedented level of control and flexibility.

Source: Gantry