Influencers: brands want them, and bloggers and others want to be them. But who are they? What do they do? How do they make money? And what makes someone a social media influencer?

An infographic published by influencer marketplace Izea answers those questions—and more.

An influencer can be anyone,from a blogger to a celebrity, the infographic explains, but they must always have credibility and a niche.

Influencers are generally compensated with money or samples. Before you pay just anyone to promote your product, however, be sure the influencers you work with match your brand's tone, style, and mission, the infographic explains.

For more on what influencers do and how they might be able to help your brand grow, check out the infographic: