What does pentesting mean?
"Pentesting is often called “ethical hacking” by those that practice it. Pentesting is a practice designed to find the holes and backdoors that may have inadvertently been overlooked when a system, server, web application or other software was put together."
May you enjoy your journey into offensive security and penetration testing - Breaking into Information Security (Gill) and The Pentester Blueprint (Wylie and Crawley).