The phrase "hidden secrets" refers to information or knowledge that is not widely known or easily discovered. It suggests that there are things that are kept secret or kept hidden from others. Full definition
It is said that in the hearts of these flowers hides the secret of youth! (funkyforty.com)
The glitch gun not only reveals a ton of hidden secrets in the environment, but can also be used on enemies to cause a wide range of different effects. (useapotion.com)
The masks add strategy and variety to the game play, and are great for players that love collecting items and discovering hidden secrets. (gameluster.com)