Peering is a really cool thing. Honestly, 90% of the time it tends to be a very beneficial process. It's when two major backbone Internet service providers peer together. They agree that transit between the two entities is free. That's in the case of settlement-free peering. There's also paid peering, where ISPs can charge lower rates for connecting directly to their network. However, in the United States, that has been used to extort companies like Netflix and other video-on-demand companies, by other ISPs refusing to peer and then making Netflix, etc., pay for the Internet transit, ultimately forcing them to cough up.
On February 8th, 2018. See this statement in context.