Mobilizon is a tool designed to create platforms for managing communities and events. Its purpose is to help as many people as possible to free themselves from Facebook groups and events, from Meetup, etc.
The Mobilizon software is under a Free licence, so anyone can host a Mobilizon server, called an instance. These instances may federate with each other, so any person with an account on ExampleMeet will be able to register to an event created on SpecimenEvent.