The Key parameter is the character representation of the key, X and Y parameters contain the mouse positions of the window at the time of the key-press A thing that we do in function in turn is toggle back and forth inside index with the same vertex data in one container.
The Key parameter contains the character representation of the key pressed, while the X and Y parameters contain the mouse positions relative to the window at the time of the key-press. The only thing we do in this function is toggle back and forth between index buffers while retaining the same vertex data.