If you want to understand some of the basic concepts behind digital photography and editing digital images, you should check out these Key Concepts pages. Each one is a very quick read. I highly recommend taking a peek before you dive into learning how to use any of these programs. Here is the list of Key Concepts for Photoshop and Lightroom:
Digital image basics
- Aliasing & Anti-aliasing*
- Bounding box
- Canvas*
- Color mode or Image mode
- Compression
- Raster & Vector*
- Resolution
- Sample
- Zoom
Layers
Photo adjustments
Special effects
Transformations
Here is the list of Key Concepts for Photoshop Elements 9:
Digital image basics
- Aliasing & Anti-aliasing
- Canvas
- Color mode or Image mode
- Compression
- Keywords
- Raster & Vector
- Resolution
- Sample
- Selection
- Zoom