The German expression Kindergarten usually refers to the first level of official education, according to the K-12 educational system. Kindergarten is usually administered in an elementary school.
The first kindergarten was opened in 1837 in Bad Blankenburg, Germany by Friedrich Wilhelm August Fröbel.
Youngsters, usually aged 4-6 attend kindergarten to learn the finer points of meeting friends (and enemies), professional authority (in the form of a teacher), playtime, naptime, drawing, music, the basics of reading and writing, and various other activites.
The youngster continues to Grade 1 after Kindergarten.
The actual word "Kindergarten", as one may guess, translates to "children's garden".