Orthodox Christianity is a form of Christianity that is descended directly from the
Apostolic tradition. Orthodox Christians argue that the
Catholic church split off from it in
1054, while Catholics argue that the reverse is true.
The organizational structure of Orthodox Christianity is far less centralized than that of the Catholic church, and local parishes have far more autonomy than those of Catholicism (indeed, the parish priest is an employee of the parishioners).
Although there appear to be many Orthodox Christian traditions (Greek Orthodox, Russian Orthodox, Ethiopian Orthodox, etc.), they differ only in the language that the services are conducted in and some local traditions.
The most important holiday in Orthodox Christianity is Easter, or Pascha, a celebration of the day when Christ rose from the dead and gave humanity eternal life.