Artifacts are mysterious and unexplained alien devices sometimes discovered on Planet. If you can find an artifact and return it to one of your bases, you will have several options: (a) you can link it to a Network Node if you have one, and receive a free technology breakthrough; (b) you can use it to speed the production of a Secret Project or Unit Prototype; (c) you can save it to use later.
Artifacts can be captured from other players. A lone artifact can be captured by any player without diplomatic penalty.