Adobe Photoshop is very easy to learn. The program is very user intuitive. The software makes it very easy to edit and create very professional looking photographs.
You mean to work with? Photoshop for sure, because you can find many free tutorials and books on Internet on how to use it. Photoshop also have best possible support for users from online Help and...
You can learn from books, Internet tutorials. There are lot of tutorials on Internet just type photoshop tutorials in browser. Good starting point are official Adobe video tutorials. See related link.
Adobe's website provides easy and often free downloads for their products, many of which are needed in today's web and business environment. See the link below for more information on downloads.