This is the 3139th most frequent Polish word.
przygotowali
"Przygotowali" means "they prepared" in English.
Here, 'przygotowali' is used to indicate that the students completed the task of preparing something (a presentation) for a specific purpose (a lesson).
Uczniowie przygotowali prezentację na lekcję biologii.
The students prepared a presentation for the biology class.
In this case, 'przygotowali' is used to express the completion of preparing a physical space (the venue) to make it suitable for an event.
Organizatorzy przygotowali salę na imprezę.
The organizers prepared the venue for the event.
Here, 'przygotowali' denotes the action of making food or drinks ready for the guests.