The commands are part of a programming language used to draw shapes, and the mentioned method is a practical approach to draw an ellipse by keeping the string taut around two foci.
An ellipse can be constructed using a very simple method that takes advantage of its geometric properties. By inserting two pins into a piece of paper to represent the foci of an ellipse and looping a string around these pins, one can trace an elliptical shape. This works because as the pencil stretches the string tight and is moved around, the sum of the distances from the pencil to the two pins remains constant, which is a defining characteristic of an ellipse. The major axis is twice the distance from the center to a point on the ellipse along the longest radius, known as the semi-major axis.
Regarding the original question, the commands given are likely for a computer program that draws shapes using specified functions. The ellipseMode(CENTER) command probably sets the starting point for drawing the ellipse at its center, and the ellipse(60,40,20,20) command instructs the program to draw an ellipse with a center at coordinates (60, 40) with a width and height of 20 units each. If this were done with string and pins, the two foci would be together, making it a circle, which is a special case of an ellipse.