Access Control

Public: This variable or function can be used from anywhere in the script
Private: This variable or function can only be used by the object it is part of; it cannot be accessed elsewhere
Protected: This variable or function can only be used by the object it is part of, or descendents of that class
Final: This variable or function cannot be overridden in inherited classes
Abstract: This function or class cannot be used directly - you must inherit from them first