This is the 6024th most frequent Russian word.
собравшихся
"Собравшихся" means "those gathered" or "assembled."
Here, 'собравшихся' is a participle form used as an adjective to describe the object 'people,' indicating that they were gathered or assembled.
Собравшихся людей попросили пройти в зал.
The gathered people were asked to proceed to the hall.
In this sentence, 'собравшимися' is in the instrumental case, used to describe the guests who gathered, emphasizing their presence at the event.
Организатор выступил перед собравшимися гостями.
The organizer spoke in front of the gathered guests.
Here, 'собравшихся' is in the genitive plural form to describe all the people who had gathered, showing inclusion in the group being referred to.