Foreshortening is distorting the object to make it appear to be 3D on a 2D surface. An ellipse would be an example of a foreshortened circle.
The circle appears squished at the sides. Which makes the circle look like its lying flat on the paper.
Notice the ellipses used to make this cup and saucer.
Here’s a foreshortened square

Did this lesson help? Let me know in the comments
Continue on to the drawing concepts