Although all Old Believers groups emerged as a result of opposition to the Nikonian reform, they do not constitute a single monolithic body. In fact, the Old Believers feature a great diversity of groups that profess different interpretations of the church tradition and often are not in communion with each other. Some groups even practice re-baptism before admitting a member of another group into their midst.
The terminology used for the divisions within the Old-Believer denomination does not always make precise delineations. Generally, people may refer to a larger movement or group — especially in the case of such major ones as popovtsy and bespopovtsy — as a soglasie or soglas (in English: "agreement" or more generally, "confession"). Another term, tolk (English: "teaching") usually applies to lesser divisions within the major "confessions". In particular it can characterize multiple sects that have appeared within the bespopovtsy movement