margin: 0 auto;

Means the text above start at 0 pixels from the left, but what automatic rest? What are some examples of what I can change the automobile?

thank you

When applied on the body or a div wrapper, the center simply content horizontally on the page. 0 applies to the top and bottom, the car left and right. It can also center the individual elements in a div, but does not mean 0px 0.