Three ways to style - There are three ways to style and add CSS to your webpage. The three ways are inline, embeded, and linked, the only one that really makes sense to do is to link your CSS file to your HTML page. A CSS file can be linked to as many HTML pages as you want which helps ensure a consistent look.
Anatomy of a CSS rule - CSS is made up of two parts, the selector and the declaration. The selector defines what part of your webpage you are going to stylize, it is the same tag that is used in HTMl. The declaration defines what will happen to the selector it is applied to. The declaration is made up of two parts, the propety which states what will be affected and the value which is what the property is set to.
Writing CSS rules - Multiple declarations can be defined in one rule so you can stylize a selector in multiple ways by only writing one tag. Selectors can be grouped which can help you avoid reptition of writing the same rule for different selectors. Multiple rules can applied to the same selector, so if ypu grouped selectors together previously but want one to be bold you can do that by writing a seperate rule for it.