I came upon this when I was messing around with TextButton's property "Active". What is it for? Thanks for reading, and/or explaining.
It is just an inhered class from GuiObject which "Determines whether a GUI element will interact with inputs such as the mouse."
To enable a gui object to move freely both the active and draggable property needs to be enabled.
My opinion is that it is a property to say weather the gui object should include the users mouse inputs. Excluding the events of course.