This document provides an overview of security testing. It explains that security testing is performed to reveal security flaws in a system to protect data and maintain functionality. The document is intended for beginners to help them understand the basics of security testing. It provides information on topics like penetration testing workflow, footprinting, scanning, enumeration, exploitation, malware, HTTP/HTTPS protocols, encoding and decoding, cryptography, same origin policy, testing cookies, and hacking web applications.