This is the 829th most frequent Russian word.
прошедшие
"Прошедшие" means "those who have passed" or "past" depending on the context.
Here, "прошедшие" is used as an adjective derived from the verb "пройти" and means "past" or "elapsed" to describe years that have passed.
Прошедшие годы оставили свои следы.
The past years left their marks.
In this sentence, "прошедших" is the genitive plural form of the adjective meaning "past" related to "события" (events).
Мы поговорили о прошедших событиях.
We talked about the past events.
Here, "прошедшие" is part of a participial phrase, referring to people who walked by with an implied "те, кто" (those who).