Controllers are what holds all the logic behind your website, you will have the main controller in your project to begin with, and it will have one function. The index function is the default function for all of your controllers. It is what gets executed if the browser does not specify what to execute.
The way functions, or methods get executed in BasicMVC is really simple.
http://example.com/model/function
The above indicates a specific model, and a specific function within that model to execute. Another cool things about models is the ability to interact with other controllers on the fly. You can load them to execute several functions, or load it and execute one functions with just one line of code.
$this->loadController("ControllerName");
The above line of code will load another controller into the object so you can interact with it. But how can you interact with it?
$this->ControllerName->function();
It's that easy. There is another way of doing this same thing in one line of code though.
$this->loadController("ControllerName", "function");
This will load an other controller into the object and execute the function defined. You can also come back and execute more functions if needed though.