This is the 1319th most frequent German word.
stellten
"Stellten" is the past tense form of "stellen," meaning "placed" or "put."
In this sentence, 'stellten' is used as the past tense of 'stellen', meaning 'to place' or 'put something in position'.
Die Schüler stellten ihre Bücher auf die Tische.
The students placed their books on the tables.
Here, 'stellten' is part of the expression 'stellen sicher', which means 'to ensure' or 'make sure'.
Die Lehrer stellten sicher, dass jeder die Regeln verstand.
The teachers ensured that everyone understood the rules.
In this case, 'stellten' is used in the phrase 'stellten vor', meaning 'to present' or 'introduce'.