What does it mean to understand something (or, someone)?
If you understand something, you understand how it will react, or respond to a particular change. There better our understanding, the more complete it is, the better we can predict the response.
It’s a lot like what scientists do. They study something, they experiment. And from their experiments, they build on or improve their model of the thing that they are experimenting on. This was something I learned in grade 7 science class, or thereabouts. Science is the process of creating models.
Science is the process of creating models.
A model represents something. It is only a representation and so any prediction it provides will have some error. However, the better the model is, the less the likelihood of error, or if there is error, the less significant that error is.
Taking a lesson from science, when we understand something we have a model of that something within ourselves.
For now we can say that this model is stored in our brain.
The better this model is, the better our understanding of the thing that it models.
Now, just imagine that we had a perfect model. Terry Pratchet uses this idea in one of his books. When we have a perfect model, what we have is no longer a model, it is the thing that it represents. We know exactly how the thing will respond or react to any change in circumstances because the model is a perfect representation of the thing that it represents.
Now there are models that you build, like scale versions of world war 2 fighter planes. Then there are theoretical models. These can be represented by equations on pieces of paper, or stored in computers. Then there are imaginary models, which are stored in our brains. All of these models represent something.
When we have the model installed in our brain we can access it instantly.