The "Savant" is a Heechee computer which resided on a planet of Aleph IV. It is an optical computer that uses a crystalline matrix for storing and processing information with three colored memory storage units.
It was left by the Heechee so that its native population could find and use it. It would teach the Heechee language, basic maths and a little history. Its primary function was to deliver a warning about the Assassins and the shield.
It was found and brought by the Gateway protagonist and interpreted by the humans for three weeks after its discovery.