As implied by the title, it allows the user to steal any reward from the winner of a Reward Challenge, with seemingly no exceptions. However, it can be used only once, so the holder will have to think carefully of what reward they would want to steal.
At the final six individual Reward/Immunity Challenge, David Wright won for himself a steak dinner at camp, as well as the right to pick two of the other five castaways to join him. Jay used the advantage and claimed the reward for himself. He picked David, the challenge winner, and Adam, who had given him the advantage, to join him on the reward.
Survivor: Edge of Extinction
During the marooning on Day 1, a secret advantage was hidden among the supplies that castaways could gather. Ron Clark found the advantage, which turned out to be an Advantage Menu giving him one of three advantages up until the third Tribal Council. The finder can either steal the reward from the winning tribe, use the parchment as an Extra Vote, or use it for individual immunity, which works similar to a Hidden Immunity Idol. Ron did not have to choose any advantage as his tribe did not go to any of the first three Tribal Councils, leaving the Advantage Menu to expire after the Day 8 Tribal Council.