What is influencer marketing?

It's sometimes easier to understand with analogies, so here you go:

It is a very popular friend basically helping you get the word out about your business. In the same way you would ask someone in your community with a big following to recommend how awesome your new product is, businesses do that too: partnering up with social media stars. These followers go on to shoutout your products and services which may otherwise be invisible in a heap of businesses trying hard to grab more customers.