For a piece of fabric, there are three important parts that you need to know.  They are the right side, the wrong side, and the selvage. 

Right side-  Just like the picture above, the right side of the fabric is the more vibrant, colorful side of the fabric.  This is the side you want to see when you want to see when you are done sewing.

Wrong side-  The wrong side is the side that is less vibrant, or less colorful.  In a solid piece of fabric, it is very hard to tell the difference between the right side and the wrong side, since they are the same color.  This is side of the fabric that we don't want to see when we're done, because it's not as nice.

Selvage-  This is a piece of the fabric that is usually on one of the sides that has been woven a bit differently.  You may also see the company's logo or copyright information.   The selvage is there because it is woven (or created) in a way that won't fray.