A room in Game Maker Studio can be a level, a menu or even credits. The built-in room editor allows for a uniquely fantastic range of level designs. Once again, Game Maker Studio shows off its ease of use with their built-in room editor. Easily change the background image, views, physics or add tiles with the room editor. Game Maker Studio allows you to place your objects into each room, while also giving you the option to adjust the view on each object (for example, if you have a particularly large room and would only like your character to be shown in part of it, you can adjust the view so that the camera is only a certain size around your character).
2 Curated Resources
GameMaker: Studio Tutorial - Episode 1, Room Creation
free, YouTube Video
Here, you can see first hand how the room editor works.
How To Create a Room With a View in Game Maker Studio
free, Website