It’s a presentation framework based on the power of CSS3 transforms and transitions(positioning, rotating and scaling them on an infinite canvas) in modern browsers and inspired by the idea behind prezi.com
Additionally for the animations to run smoothly it’s required to have hardware acceleration support in your browser. This depends on the browser, your operating system and even kind of graphic hardware you have in your machine.
For browsers not supporting CSS3 3D transforms impress.js adds impress-not-supported class on #impress element, so fallback styles can be applied to make all the content accessible.