I am a web designer and I use photoshop everyday. It's a great tool to edit photos: you can edit images, resize and retouch pictures, make collages, apply cool effects, ecc. It's a professional tool but you can still use it if you are a newbie to make basic graphic things like resizing and cropping images, change colors. etc.
You can download a free version of photoshop here: http://bitly.com/1p34aA3
Give it a try.