Chapter 1 - Introduction to Computers, Programs, and Python - Section 1.9 - Getting Started with Graphics Programming - Check Point - MyProgrammingLab - Page 24: 1.42

turtle.done() causes the program to pause until the user closes the Python Turtle Graphics window.

Line 33 invokes turtle’s done() command, which causes the program to pause until the user closes the Python Turtle Graphics window. The purpose of this is to give the user time to view the graphics. Without this line, the graphics window would be closed right after the program is finished.