Inheritance means the styles of one set of tags is inherited by another set of tags. For instance, say you have a style named Bob that's defined like this:

.Bob { font-family: Arial; font-size: small; }

Then you applied the style to the body of your HTML document like this:

<BODY class="Bob">

Every other tag within the body will inherit the properties of the style sheet Bob. This means all the text would appear as Arial and be small. Now, suppose in the same document, we have a second style named Dave:

.Dave { font-size: large; }

And then say we applied the style Dave to a paragraph within the body tags like this:

<BODY class="Bob">
   <P class="Dave">Hello</P>

What would happen? Because tags within the body inherit the Bob style, the word "Hello" would appear as Arial. However, since the properties of Dave override the properties of Bob, "Hello" would appear large, not small.