People often confuse inheritance with the cascade. Although they seem related at first glance, the two concepts are actually quite different. Luckily, inheritance is a much easier concept to grasp.
Certain properties, such as color or font size, are inherited by the descendants of the elements those styles are applied to. For instance, if you were to give the body element a text color of black, all the descendants of the body element would also have black text. The same would be true of font sizes.