You probably have a sticker on your car that is required for you to park in the company parking garage. Company policy might require you to get a new photo taken each year for your company ID badge. You might distribute keys for the equipment room to several of your employees. Physical security is something that most of us deal with every day.
CISSP candidates studying the physical domain must understand what is involved in choosing a secure site. The candidate must also have knowledge of the methods used to secure the facility and, most important, how to protect its resources and employees. The goal of overall physical security is to deter, delay, detect, assess, and respond.