Gameplay mechanics play a huge role in games we play. Without them, you would have a game with no interaction. You might as well well look at an image or watch a movie. This section of development is what happens behind the scenes and is responsible for logic being implemented.
The easiest way get beginning coders to understand gameplay is to mention loops and if statements. From when you start a program you are in a loop. The program waits for you to press a button via loop. If a button is pressed, an if statement checks which button is being pressed. Depending on which button has been pressed an action is performed. Games are a compilation of systems that are just loops and condition statements. Video games are more than that but this true at the surface level.