This explanation has been borrowed freely from Patrice Miller’s site http://www.webbitt.com/volga/paroch.html

Parochial Certificates are the official documents provided by the Lutheran and Reformed pastors to families moving away from their home church. The parochial certificates for the Volga Germans are generally written in German or Russian or both.

Philip Freimann provides this concise summary of the purpose of the certificate: “I was told that the purpose was for the "sending" pastor to tell the "receiving" pastor / church in the new country that this family was in good standing, having been baptized, married, taken regular communion, etc. Something we would call a "letter of transfer" today.” Some of the documents were totally handwritten and some relied on a preprinted form. The purpose of these certificates was so people could get married and join a church without having to write letters back and forth between the different churches. One had to have the certificate to get married and join a church according to Horst Gutsche.

Obviously these meticulous records were extracts from the church books. We know the Huck church books exist in Russian archives for the period 1767 through 1845. The availability of church books for Huck after that period is unknown.

The examples from Paul Lais illustrate how the document can be a mixture of Russian and German text. The example from Dennis Zitterkopf illustrates one of the handwritten documents. The confirmation certificate for Alexander Lais is another example of a document type describing an individual’s prior association with a church.

An exchange on the GERVOLGA mail list and summarized by Patrice Miller indicated these travel documents were not issued for Catholics even though the same type of information was included in Catholic church books. During the exchange, it was occasionally mentioned that the documents had a second unintended purpose for many of our ancestors and that they were used in the same fashion we use birth certificates as proof of identity to obtain passports, to travel abroad, etc.

It does not appear that the certificates were issued for that purpose because what government agency needs to know when someone had their last communion or knew the scriptures? But they were probably a valuable form of identity in a foreign country where a traveler had very few identifying documents except for their passport. So this was an unintended benefit of having the document.