What did the maze code reveal?

The maze code revealed that there was a secret door to exit the maze.

"There's a computer station in a place we've never looked before. The code will open a door for us to get out of the Maze. It
also shuts down the Grievers so they can't follow us — if we can just survive long enough to get to that point."

Thomas also sees glimpses of the creators assembling Theresa, who is a robot sent to spy on the Gladers as part of the original experiments. He also sees his family and brother being taken away and killed in front of him by the creators and Theresa as a way to force him to keep working on the Maze and the variables.