This lesson is a two part video tutorial on the basics of working with layers and masks in photoshop which will give you much more power and control on making specific adjustments to your images.
The first segment teaches you the difference and how to create transparency layers, adjustment layers, text layers, and duplicate layers in photoshop.

The second segment teaches you how to create and use layer masks in photoshop.

https://www.skillshare.com/classes/photography/The-Basics-Of-Understanding-Layers-And-Layer-Masks-In-Photoshop/935491627