A monk or nun is one who has taken the vows and received the tonsure of monasticism. In the Eastern churches, unlike in the West, there were never developed separate orders. Rather, each monastery developed its own rhythm and order with certain commonalities among all Orthodox monasteries.
There are various ranks of monks and nuns, varying according to the tradition of the region. Generally speaking, there are two broad categories of monastic traditions, the Russian (Slavic) and the Greek (Byzantine).
Generally, it can be said that there are four levels with regards to monks; although even what these levels mean can vary from place to place.