Prudential means “to do with being careful and looking ahead,” almost always in formal, legal, or money settings. A prudential rule is a rule made so a person, a bank, or a company does not take a foolish risk. In ordinary talk most people just say prudent; prudential sounds like a document, a regulator, or a meeting. You will also see Prudential as a company name (an insurance firm), which grew from the same idea of looking after the future — in Taiwan that brand is 保德信 — but the adjective itself is not a brand. The dictionary’s short gloss “prudent” is close, though actually prudential is narrower: it often names the kind of caution, or the rules for that caution, rather than a person’s everyday habit.