What the Korok mask Does in Breath of the Wild – DLC Pack 1 | Austin John Plays
It allows Link to detect the unnamed Koroks who are hidden throughout Hyrule and offer a Korok Seed when discovered. When a hidden Korok is nearby the mask will produce petals (like those produced by some hidden Koroks) and make adorable Korok sounds, with the mask shaking and its pinwheel will spin.