Unless you just happened to accidentally stumble in here, you probably already know what Photoshop is and you're here to increase your knowledge or look for a solution to a nagging problem.

With that deep stuff out of the way, here's a short and highly truncated list of some of the things Photoshop CS is capable of :

• Fix images with poor color or lighting conditions. Improve detail and clarity in washed-out images or reveal parts of an image hidden in shadow.
• Remove the dreaded "red eye."
• Repair old photographs. Fix up grandma and grandpa's wedding photos!
• Creating photo composites. Remember, in elementary school art classes, when you would cut photos out of magazines and paste them together to create a new composition? Imagine being able to do that again but having the power to make it look real.
• Combine multiple photos together to create a panoramic photograph.
  Easily print a contact sheet to fit as many photos as possible of your daughter's first day at school onto a single sheet of paper.
• Create business cards, letterheads, logos, flyers, newsletters, and posters using images and text.
• Use built-in filters and styles to easily apply various effects to your images and text.
• Anything else you can imagine, Photoshop CS can probably do.
  
  This Photoshop Reference Guide consists of the following areas :
• Basics and Setup
• Color Management
• Layers
• Selections
• Masks
• Channels
• Paths and Shapes
• Painting and Brushes
• Type
• Color and Value
• Filters
• Restoring, Manipulating, and Compositing
• Saving and Exporting
• Actions and Automation
• Building Web Graphics with ImageReady
• Working with Adobe Version Cue
  Source : informit.com