

Baptism
Mennonites are a free Protestant church with its origins in the
Anabaptist movement of the early reformation age.
The Anabaptists, emerging in 1525 in Zurich, Switzerland,
disapproved of infant baptism and practised adult baptism of
believers instead; the foremost reason they were called Anabaptists
(re-baptised). They preferred to call themselves "Brethren in
Christ".
Even today, baptism of believers denotes a cornerstone of Mennonite
communities. Baptism preparation classes are offered to build a
basis for church membership.
The name "Mennonites" is derived from Menno Simons (1496-1561), a former Catholic priest, who joined the Anabaptists and became one of their most important leaders
If you would like to find out more about Mennonites, please contact a local congregation or obtain the booklet "Typisch Mennonitisch”, ed. Paul Warkentin and Dieter Goetz Lichdi or the booklet "Mennoniten. Ansichten einer Freikirche", at
Arbeitsgemeinschaft der Mennonitengemeinden in Deutschland
or
Bund der Europaeischen Mennonitischen Bruedergemeinden
As English native speaker, you may also look for John Howard Yoder's "The Politics of Jesus".
Of course you will find elaborate information in the internet using Wikipedia taking the key words Mennonites or Anabaptism.