- mrsstrlSeptember 2020
Probably you mean PLZ, the akronym for Postleitzahl (Почтовый индекс). There's nothing to teach about, just looking for it.
The leading number loosely is correlated to the state from which the Federal Republik is constructed, so as to 1 for Berlin, 2 for the Hansecities etc. up to 9 and 0 for the former Германская Демократическая Республика (You remember those partner of your country?), because the system is in effect the expansion of the old 4-figures-scheme of BRD up to 5 figures now.
Additionally there are special numbers for big enterprises and government mail although they have mail adresses with street names also.