 I went to draw a rectangle that is 50 pixels tall, and that is twice as wide as it is tall. How would I program the computer to do that? Well, I could tell the artist to go up 50, turn right, and then go over 100, and loop the whole thing twice. But then I'm doing the math for the computer. Multiplying 50 by 2 in your head may not be that hard, but computers are really good at doing math. So we should leave it to them whenever possible. If I just used a variable called height instead, then I could easily change height to 50 and then change my algorithm to tell the artist to go up by height, turn right, and then go over by height times 2, which gives us a rectangle that is twice as wide as it is tall.