OpenGL Programming Guide: The Official Guide to Learning OpenGL, Version 4.3, Eighth Edition

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Up to this point, all of our discussion regarding buffers has focused on the buffers provided by the windowing system, as you requested when you called glutCreateWindow() (and configured by your call to glutInitDisplayMode()). Although you can quite successfully use any technique with just those buffers, quite often various operations require moving data between buffers superfluously. This is where framebuffer objects enter the picture. Using framebuffer objects, you can create our own framebuffers and use their attached renderbuffers to minimize data copies and optimize performance.

Framebuffer objects are quite useful for performing off-screen-rendering, updating texture maps, and engaging in buffer ping-ponging (a data-transfer techniques ...