micro-influencer

Kim Kardashian is an influencer with 341.9 million followers.  A micro-influencer typically has between 3,000 and 10,000 followers BUT they are serious followers who share a niche interest and are convinced of the integrity of the micro-influencer and the value of the information provided.

This means that if a brand wants to target a particular group of people, a micro-influencer or a set of such influencers may be of more interest to them than the herd following of a Kardashian.  They can be more confident of getting the attention of the niche group and more confident that the group will believe their influencers when they say that the brand is good. If the influencers are paid by the brand for the promotion, they need to make that clear or they stand to lose the trust of their followers.