A social media influencer is a user on social media who has established credibility in a specific industry. They are people who have built a reputation for their knowledge and expertise on a specific topic and make regular posts about that topic on their preferred social media channels. They have a following in a distinct niche, with whom they actively engage. Social media influencers establish themselves as opinion-leaders with their followers and may have persuasive strengths such as attractiveness, likeability, niche expertise, and perceived good taste. They have the power to affect the buying habits or quantifiable actions of others by uploading some form of original—often sponsored—content to social media platforms like Instagram, YouTube, Snapchat, TikTok or other online channels.

Influencer marketing is when a brand enrolls influencers who have an established credibility and audience on social media platforms to discuss or mention the brand in a social media post. A social media influencers personal brand and product relation with marketers are important concepts. It is important to note that these individuals are not merely marketing tools, but rather social relationship assets with which brands can collaborate to achieve their marketing objectives.