If you make sure that a Pokemon with the Compound Eyes ability (or, new to Sw/Sh, the Super Luck ability behaves the same way) is in the first slot as the battle begins, an opposing species with a 5% chance to hold an item has that chance upped to 20%, and 50% chance hold items become 60%. If it's not actually in the first slot, and was either switched in or preceded by a fainted Pokemon, those abilities have no effect.