It's multiple things: - the pattern library, a set of design guidelines (http://www.patternfly.org http://www.patternfly.org) - Patternfly Core, the HTML+CSS

It's multiple things: - the pattern library, a set of design guidelines (http://www.patternfly.org http://www.patternfly.org) - Patternfly Core, the HTML+CSS implementations (Bootstrap-based) - Framework integrations for React, Angular 1 and Angular-NG. They're currently working on pf-next, which will no longer be based on Bootstrap and feature a new design. (Disclaimer: not affiliated with Red Hat)