This is the 18041st most frequent Russian word.
фотовыставку
A photography exhibition.
The word "фотовыставку" is in the accusative case here, indicating that it is the object of the verb "посетил" (visited).
Я посетил большую фотовыставку в музее.
I visited a large photo exhibition in the museum.
Here, "фотовыставке" is in the prepositional case, showing the location or context of the action.
На фотовыставке представлены работы известных фотографов.
At the photo exhibition, works of famous photographers are displayed.
In this sentence, "фотовыставку" is in the accusative case as the object of the verb "организуем" (organize).