Hi Alex! This is basically a "Yes, and..." mechanic where players use their Perception to build the world around them. The point is you roll to check for whatever you have in mind and if the roll is successful, whatever you were looking for is there, then you lower your Perception level. If the roll fails, you increase it instead. That way sometimes it will work, and sometimes it won't. It's very basic, technically you could even replace the dice mechanic with a coin flip and it wouldn't be exactly the same but from the players persective it might not matter much, I just like throwing dice better than flipping coins.