If your parents both had red hair and green eyes, then it is very likely that you and your brothers and sisters have them too. There is also a pretty good chance that some of your children will have the same family characteristics. They will have inherited them.
Inheritance also plays a major part in the way that styles work on a Web page. Think of the <body> of the page as being the parent. Okay, it's a one parent family but that's not unusual these days.
Any other items, the siblings, placed within the <body> should adopt the same characteristics as the parent by default. I say 'should' because that's the way it is supposed to work. In practice, some browsers just don't play the game - and there's your first 'gotcha'. Current browsers are inconsistent in the ways they handle the same style specification. The newest browsers are better, Netscape and Explorer 6, Opera etc. Netscape 4.x is pretty bad and ones earlier than that you can just forget about - luckily, they are now very rare.