Actors: nation-state, organized crime, hacktivist, insider, unskilled attacker, shadow IT

A threat actor is the person or group behind an attack. Security+ asks you to identify actors from a scenario and to understand how their resources, sophistication, location and goals shape what they do. This matters in practice because defending against a teenager with downloaded tools is very different from defending against a government intelligence agency. Threat intelligence reports describe actors in exactly these terms, and risk assessments use them to decide which scenarios deserve the most money and attention.