What does non-white in calligraphy mean?

It's called Feibai in calligraphy. That is, dip a pen in a little thick ink and write faster on the paper. So that in some places in the middle of the writing path, a little blank appeared. In this way, I am idle, and my words are vigorous and powerful. Give the observer a natural artistic beauty. It's called flying white. It should be noted that this method should not be used in many ways, which makes people feel boring.