It's a server that storage all events do you give, in the Relay, have a lot of peers connected to him, your event is seen by other peers, and the events of the other peers will be viewed by you, if you leave this Relay, you can't see the events of their peers anymore, and they too about yours, but, all the events that you give to the Relay, if de Relay's admins don't delete, your past posts can be viewed by the peers that continues connected to the Relay.