Objective-c - What is the role of CGContextSetTextMatrix in CoreGraphics?

Question

CGContextSetTextMatrix(context, CGAffineTransformIdentity);

What is the specific function of this sentence? I searched a lot on the Internet and most of them said "Set the glyph transformation matrix to CGAffineTransformIdentity, which means that each glyph does not undergo graphics transformation"? ? ?

The explanation is so abstract, is there any way to explain it more vividly?