The Hideout is a level in Sly Cooper and the Thievius Raccoonus which serves as the world select screen.
In Sly 1, you enter the Hideout for the first time after completing the tutorial level, Paris, France. Bentley will explain that you can watch any unlocked cutscenes on his computer, then give a brief tutorial on how to move around the Hideout.
Sly is not present in the Hideout. Rather, you directly control the camera by scrolling left/right to move between each world map in the game. Initially, only Tide of Terror is unlocked. You may scroll to the next locked world in the game, but it will be obscured by Murray, who has a unique animation for each locked world.
Once all five worlds are unlocked, you may scroll freely in a full circle around the Hideout, and Murray will take a seat beside Bentley's desk.
Hidden out of bounds behind each world map are collections of cubes arranged in a 3x3 grid. Each world has a number of cubes equal to how many levels it has. The purpose of these cubes is unknown.