Comprehension usually used with of. Understanding is a relation between the knower and an object of understanding. Both comprehension and understanding can be used to talk about someone's ability to understand something.
How is digitalization challenging traditional journalism? by
The meaning of understanding is a mental grasp : How to use understanding in a sentence. Or about how something works:
Understanding implies abilities and dispositions with respect to an object.
Your understanding might be that your mother will always drive you to school if you miss the bus. Understanding a concept means you get it. He noted bond's apparent lack of. Knowledge about a subject, situation, etc.
