Basically, it's a project where several writers get together and create a world wherein they can all write stories using the same characters and backgrounds. It differentiates from corporate projects like movie and TV universes in that those properties are designed to be ongoing serials done by work-for-hire writers, and the shared world projects are open to all interested parties. Some of the best known in SF and Fantasy were THE TALES FROM THE VULGAR UNICORN and the WILD CARDS series. Besides the two furry shared universes mentioned by GreenReaper (which are both still ongoing), there was the FURKINDRED, published by MU Press over a decade ago; three volumes of comics and prose were published, plus one stand-alone comic adventure, and two independently published short stories (one by myself, and the other by the late Gerald Perkins).
Basically, it's a project where several writers get together and create a world wherein they can all write stories using the same characters and backgrounds. It differentiates from corporate projects like movie and TV universes in that those properties are designed to be ongoing serials done by work-for-hire writers, and the shared world projects are open to all interested parties. Some of the best known in SF and Fantasy were THE TALES FROM THE VULGAR UNICORN and the WILD CARDS series. Besides the two furry shared universes mentioned by GreenReaper (which are both still ongoing), there was the FURKINDRED, published by MU Press over a decade ago; three volumes of comics and prose were published, plus one stand-alone comic adventure, and two independently published short stories (one by myself, and the other by the late Gerald Perkins).