What is the best term for used to influence people to believe, buy, or do something?

The best term that accurately captures the concept of influencing people to believe, buy, or do something is "persuasion." Persuasion specifically refers to the act of convincing someone to adopt a certain belief or to engage in a specific action through reasoning or emotional appeal. It's a broad term that encompasses various methods and techniques aimed at influencing individuals' thoughts or behaviors.

While propaganda can also be used to influence people's beliefs and actions, it often carries a connotation of manipulation or misleading information, particularly in political contexts. Advertising and marketing are closely related to persuasion, but they generally refer more to the specific practices and techniques used in commercial contexts to promote products or services. Persuasion, however, can apply to a wider range of scenarios beyond just commercial intent, making it the most appropriate choice in this instance.