Hi guys, I am currently learning MVVM and have a few questions for anyone who has taken the time to look it up.

The first is this thing of passing classes to other classes, any of the video examples I have seen do something like this:

Code:
public class viewModel
{
     readonly dataModel _model;
     
     public viewModel  (dataModel model)
     {
          _model = dataModel;
     }
}
and then they proceed to databind to the viewmodel properties but if the class is read only how do they send data back to it? Is it just a case that they are not sending back data in that instance?