The Room of Requirement takes the form of anything that the seeker needs without breaking any fundamental laws like Gamp's Law of Elemental Transfiguration. However, while it presents itself differently for different people, it does sometimes present itself in the same form as in the case of students seeking the Dumbledore's Army meeting room. The same goes for hidden things. Over the years, this room has been used by almost everyone who is aware of it to hide things and when someone seeks a room to hide something, the Room of Requirement presents itself as the Room of Hidden Things.