2013 D&C Manual Published by Church: Urim and Thummim is an instrument that aids a seer in the work of translation.
Doctrine and Covenants and Church History: Seminary Teacher Manual (Salt Lake City: The Church of Jesus Christ of Latter-day Saints, 2013, 2017), 49
What items did Moroni entrust to Joseph Smith? (the gold plates, the Urim and Thummim, and the breastplate. Explain that the Urim and Thummim is a divinely prepared instrument that aids a seer in the work of translation and in receiving revelation.)