3.3 What is a model folder?

Once you've successfully started your first simulation, you should be able to find the folder for this new project in the phetsims directory. In our case, it is called newton-raphson

But wait, I smell a very important question in the air

Question: What even is a model folder?

Answer: One important thing to remember is that this framework uses components (sliders, panels, radial button groups etc.)  to make up the simulation and these components are basically classes and we can make use of these classes by making an instance of the class (creating an object). In the same way, you will be creating components of your own using a lot of these prebuilt modules or classes. Keeping all that in mind, the model folder is the place where you keep the JavaScript files of the classes for different models you might need for your particular project. A good example of this is the least squares regression simulation by phetsims which can be found at: https://github.com/phetsims/least-squares-regression

If you look at their model directory structure it looks something like this:

In their particular project's case, they had a model to represent a Data point, a Data set, a Graph, and a Residual. Note: Each simulation already has the *simulationName*Model.js file

Hopefully that gives you some insight into what the model folder is all about.