Portal:OpenGL Objects/Renderbuffer Objects
A Renderbuffer Object is an object that represents a single image of a specific Image Format. Such objects can only be used as render targets for Framebuffer Objects; they cannot be read from, outside of any operation that reads from the Framebuffer that the renderbuffer happens to be attached to. They are only useful if you need a particular image for rendering to, such as wanting to render colors to a texture, but needing a depth buffer for Depth Tests. The depth buffer could be a renderbuffer rather than a texture.