A CSS rule-set consists of a selector and a declaration block:
The selector points to the HTML element you want to style.
The declaration block contains one or more declarations separated by semicolons.
Each declaration includes a CSS property name and a value, separated by a colon.
Multiple CSS declarations are separated with semicolons, and declaration blocks are surrounded by curly braces.
In this example all <p> elements will be center-aligned, with a red text color:
pis a selector in CSS (it points to the HTML element you want to style: <p>).
coloris a property, and
redis the property value
text-alignis a property, and
centeris the property value
You will learn much more about CSS selectors and CSS properties in the next chapters.