The picture below is of the car washed and clean ready to be Clayed, You would think this is good but its still not clean enough and still has Oxidation and dirt with in the paint that a wash will not take out. As you see the trees are blurry looking and not clear at all.

Clay bar before in use prepping for polishing then wax. Clay Bar takes all pollution & little in bedded rocks plus  Oxidation thats in the paint that will prevent a deep glossy look .

Now the Clay Bar used on paint as you see it has some brown thats all the pollution & Oxidation and little in bedded rocks that it picked up , Now the paint is ready to polish or compound witchever is needed. 

Now the picture below polish with the removal  of swirls and minor scratches allowing a deep Glossy wet look that we all seek. I must say it was a cloudy day but still looking great and your able to see the trees reflecting and looking sharp not blurry and soft to the touch