The term "posterior" refers to the back side of an organism or object. In anatomy, it is used to describe structures that are located towards the rear of the body. For example, the spine is posterior to the sternum, meaning it is situated behind it. In everyday language, "posterior" can also refer to the buttocks or rear end of a person. This area is important for various functions, including movement and balance. Understanding the posterior aspect of the body is essential in fields like medicine and physical therapy.