The display mode button looks like a square and a rectangle overlayed together. Click this to toggle between the two types of display mode.

The default display includes the outer frame of the guide with all the buttons and controls. There is also a Mini-Mode which will remove these elements and strip the guide down to the bare essentials.

To revert back, right click anywhere on the guide frame and under Window Settings select Show Guide controls. This will only bring them back temporarily. To make the switch permanant you have to toggle the Display Mode button again.