An ambassador, from a marketing perspective rather than a diplomatic and political one, is a person who acts as an outward face for the brand. Someone who speaks well of the brand and perhaps even spreads that message through their network and social channels. Some influencers do collaborations and some become ambassadors. This suggests a deeper collaboration than just putting up a post now and then. As an ambassador for a clothing brand, for example, you model the campaign that rolls out on TV, in magazines, on in-store signs and out on the town while spreading the word on your social channels.