As the image above states, participants' payments will be based on member engagement, especially the number of "claps" you give them. You know how you can leave Reactions other than Like on Facebook? Well, Medium has its version of Reactions and Like called "clap." Writers and publishers get a bigger percentage of your membership fee the more claps you leave their locked posts.

In his announcement, Medium head of product Michael Sippey said they're at the "early days of what [the company] consider[s] a grand experiment." Medium will send out more invites in the future, and anyone interested can sign up to be part of the waitlist.