If you’re asking that question, then you’re probably not being paid thousands of brands for every Instagram post or Snapchat story featuring a brand.

Social media has given birth to a new media persona: the influencer. These online personalities have built a following and then use the large number of people that subscribe to their blogs and YouTube channels or follow them on Facebook and Instagram to command fees to promote products or services to their audience.

Just like TV shows might conspicuously feature a soft drink bottle on a character’s desk or take a brand new car model out for a spin, brands are trying to put their name and image in front of audiences on social media. The value of these platforms to marketers has grown because the younger the consumer, the more likely they are to spend time online instead of in front of a flatscreen TV or flipping through a glossy magazine.

But while there are relatively few print periodicals and television network to choose from, there is a limitless supply of individuals with online followings. Not only can brands look at the total number of followers these folks have, but they can target specific influencers that resonate with the demographic they’re trying to reach.

Using celebrities to promote products is nothing new. What’s changed is who gets defined as a celebrity. It’s no longer limited to athletes and movie stars; anyone who creates content that connects with a loyal audience can start building their value as an influencer.

This decade has seen social media influencers transform how brands promote their products and spend their money – there are lots of case studies showing just how effective a single post from an influencer can be. The key to the success of this new advertising medium is the authenticity that an influencer brings and the persuasiveness of their endorsement. Since followers think of these influencers as trusted sources, it’s like getting a recommendation from a friend or coworker, not just some random review on the Internet.

But being an influencer doesn’t necessarily require millions of followers. Micro-influencers can start getting paid for posts once their followers get into the thousands. It might not be enough to quit your day job, but it will probably buy you some nice dinners or fund a shopping spree.