Your character is what you do, why you do it, and how you feel about it. A model of someone’s character is an estimate of the qualities that predict what they will think, feel, and do in a given situation.
Human beings are astonishingly adept at modeling other people. Artificial intelligence models are used to apply past observations to future decisions and actions, just as we model the character of other people to be able to predict or replicate what they do. AI model creation and usage requires many complex calculations and extremely advanced equipment. Amazingly, humans seem to have the ability to model the character of other humans with far less.
If you know an average person at least marginally, you will be able to predict their actions and desires to an astonishing degree of accuracy even if your knowledge of their lives is limited. For example, you could probably predict whether someone you knew even slightly would enjoy a particular movie or book.
Without ever thinking about it, you have probably managed to build a predictive model of the character of every person you know, and you use these models every single day to inform how you interact with others in order to obtain what you want.
On the one hand, your ability to model others is a skill so deeply ingrained that you can use it without even thinking about it. On the other, because the majority of supposedly Christian churches teach that the gospel exists in order to excuse us from being more like Jesus instead of enabling us to be more like him, you’ve probably never used these abilities to build or apply a model of Christ.