ASL STEM

Definition

When you hook up a new display to your Mac, it won't necessarily run at the right resolution right away especially if you don't restart. It might also happen if it is a weird resolution, like an HDTV. There is a feature in the Display preferences and in the display menu called "Detect Displays". It usually finds the right resolution automatically.

Source: http://tips4mac.blogspot.com/2008/08/detect-displays.html