Let all points from the graph "drop" on the x axis. The interval on the x axis covered by the falling points represents the domain. 

Let all points from the graph "slide" on the y axis. The interval on the y axis covered by the falling points represents the range. 
CONCEPT CHECK: WORD PROBLEM
The following diagram describes a student's journey from his home to a friend's house and back.The total distance traveled in the 8 hours is: miles.