Skinning is the process of changing the appearance of a Flex component. By changing a component's skin you have more control over the appearance than by using the provided properties.
Thanks for your reply. It is very helpful but I have a question. Could you please explain how to change a component's skin. Actually I did not get this point.
If you look at Day 5, you will see some good videos and exercises that talk about Introducing Skinning, Creating and Applying Skins, Skin States, etc. I would recommend starting with that.