Onionoo is a web-based protocol to learn about currently running Tor relays and bridges. Onionoo itself was not designed as a service for human beings---at least not directly. Onionoo provides the data for other applications and websites which in turn present Tor network status information to humans.
Onionoo users should head over to https://metrics.torproject.org/onionoo.html to
learn more about using Onionoo.
Onionoo service operators should read INSTALL.md.
Onionoo contributors should start reading CONTRIB.md and, once it's
available, run ant doc and read the generated JavaDocs.