There are some people who may get confused between knowing and understanding because they assume that this is the same thing. These are not the same. When you say knowing, this means that you have already gathered some facts and information about something. You may have verified the facts already so you know the details to be true.
When you say understanding, this is a type of process wherein you would think about all of the different details that you have gathered and made sure that if you would be asked to explain the process, you would be able to explain it fully because you understand everything about the topic.