VisualForce Basics

{! } - Anything inside this format is used to assign values dynamically

$- Prefix is used to denote global action

& - character is the formula language operator that concatenates strings.

$Resource - For static Resource
URLfor() - For combining zipped static resource

*when the {! contacts } expression is evaluated. On this page, Visualforce translates that expression into a call to your controller’s getContacts() method.
The getContacts() method is called a getter method