Photoshop has a lot of features like being able to slice up a web design into html. The best way to get a strong overview of Photoshop's features is to watch these instantly viewable video tutorials on the basics of Photoshop. Reading the manual to learn something new in photoshop takes a long time. Watching someone else do it and narrate what they're doing as they perform the steps is the fastest way to learn.
Here is the link to the best site I've found to learn the basics of photoshop