Explain this article to me?

It means that if the parents of the child have a trait that is inherited through a recessive gene (for example if the both have blue eyes or red hair) then their kids can only have the same recessive trait (blue eyes or red hair) . In other worlds: blue eye and red headed parents can only have kids with blue eyes and red hair. However, this statement doe not stand for dominant traits (brown eye and black hair) and these parents CAN have blue eye and red headed kids (if they are heterozygous).