Lesson 1: Elements,Properties, and Selectors--Oh My!
You should go through the tutorial on http://w3schools.com if these words aren't familiar to you, but I'm gonna put a mini-glossary here in case you don't have the terminology down.
Element-Any HTML or XML tag and it's closing tag. Sometimes referred to as a node.
Properties-A CSS style attribute. There are lots of properties so either get a reference book or keep a online reference handy.
Selector-In CSS this precedes the list of properties in the curly braces. Basically it links the CSS properties to elements.