objective-c - What does the CGRectApplyAffineTransform function in CoreGraphics do?

Question

CGRect rect = CGRectMake(0, 0, 300, 200);
        
rect = CGRectApplyAffineTransform(rect,
                                          CGAffineTransformMakeScale(1, -1));
cgPath = CGPathCreateWithRect(rect, NULL);

What does this code mean?