Some of the corrections we'll cover in this lesson include: There are various corrections that can make your images look dramatically better.
For example, some images may be too bright, while others may be too dull. As you start to gain more experience with Photoshop, you may notice some recurring problems with images that you'll want to fix. Images that come straight from a digital camera aren't always perfect.
en/photoshopbasics/understanding-layers/content/ Introduction