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 CS:GO Pass become a kind of collectible item, such as CS:GO Collectible Pins.
On DMarket you can replenish your inventory not only with CS:GO skins, but also with Dota 2 items. Take this opportunity!