Valve regularly conducts special events in its mega-popular shooting game. They are time-limited Operations with unique game modes and maps. To participate in them, players have to buy Access Pass. After the event is finished, an unused CS2 Pass become a kind of collectible item, such as CS2 Collectible Pins.
On DMarket you can replenish your inventory not only with CS2 skins, but also with Dota 2 items. Take this opportunity!