This is the 15797th most frequent Russian word.
продаже
The Russian word "продаже" means "sale" (dative/prepositional case of "продажа").
Here, 'на продаже' indicates that the items are for sale, and 'распродажа' refers to a sale event.
В этом магазине идет распродажа, все товары на продаже.
In this store, there's a sale; all items are for sale.
'На продаже' in this sentence specifies that the apartment is available to be bought.
Эта квартира уже на продаже, вы можете ее приобрести.
This apartment is already for sale; you can purchase it.
Here, 'продажей' (instrumental case of 'продажа') describes the activity or business of selling cars.