What about layers aren't you getting? I might be able to help. I could send you a couple of files that might give you some insight into how layers work and/or can be used. Try this exercise and see if it helps.
1. Find a picture of a Disney character on the on the web. One of the characters walking around the park.
2. Copy the image and past it in to a new project. Paste the image in again so you have 2 identical layers.
3. Highlight the top layers in the layers palette and remove the color from it. Don't turn the entire project B & W(grayscale) just the one layer.
4. Carefully erase the character on the black & white layer allowing the color one to come through.
domthirteen at cox dot net if you want me to send you a file of this.