Jibe is a multiuser 3D virtual world platform developed by ReactionGrid that allows users to design and host customized virtual worlds using the Unity3D game engine. ReactionGrid provides the Jibe platform technology as well as content development, project management, and custom virtual world solutions for clients such as NASA, IBM, and various universities. The document discusses what Jibe is, its architecture, using the Unity3D editor to build worlds, and additional features and support offered by ReactionGrid.