If you can master the concepts of selections, layers, and masks, you can go a lot further and a lot faster than trying to remember "steps" on how to do many advanced techniques that has intimidated many designers from moving from basic to more advanced editing and compositing with ease.
To get you started, knowing that any kind of mask regardless whether it is digital or not will show, hide or protect what is under it will help to take the mystery out of learning these concepts. You will see that these concepts can be thought of as a mask that will help you learn and apply them easier and more intuitively.