What is the Definition of a PSA or Public Service Announcement?

a short message, broadcast, or video commissioned by a government agency or non-profit organization in order to raise awareness about an issue of public interest.

A public service announcement (PSA) is a message in the public interest disseminated by the media without charge to raise public awareness and change behavior. Oftentimes these messages feature unsettling imagery, ideas or behaviors that are designed to startle or even scare the viewer into understanding the consequences of undergoing a particular harmful action or inaction (such as pictures of drug users before and after their addiction or realistic skits of domestic violence situations) as well as the importance of avoiding such choices.