Everyone understands something at every moment in his own way. But understandingmay be larger, and larger, and still larger. In this sytem we call understanding a certain possible maximum on a certain level of knowledge and being. You should think of why you come here, what you want from this system and why, what you can learn from it, why this sytem exists, why I talk about this system, what I wish to achieve by talking about it. There is no 'real' understanding.
Understanding is relative.
It is like temperature, it may be five degrees, ten degrees, fifteen degrees. Because in ordinary language all words are taken as absolutes. In reality there are differnt degrees of understanding. As I said, we can understand better, and still better. This conviction that in order to understand something it is necessary to define it is quite wrong, because most things we cannot define, and the few that we can, we can define only relatively with the help of other things.