What is "catechismus"

Catechismus in der windischenn Sprach or shortly Catechismus ( Catechism, also known as or shortly in modern Slovene), is a book written by the Slovene Protestant preacher Primož Trubar in 1550. Along with Trubar's 1550 book, Abecedarium (Abecedary), Catechismus was the first book published in Slovene. Catechismus served as part of a foundation of the establishment of a national identity for Slovenes.