Collections are a selection of CS:GO skins produced by Valve. A total of 26 collections have been released by Valve with the most recent being the Blacksite Collection, 2018 Inferno Collection and 2018 Nuke Collection which were released in 2018.
Active Collections drop skins through the weekly drop scheme.
In-active Collections are not available through the weekly drop scheme. The skins from these collections can only be acquired through opening souvenir packages or gift packages, or through trading and the Steam Community Market.
Operation-exclusive Collections drop skins through the weekly drop scheme only to those players who have the current CS:GO operation pass. These collections have been exclusive to operation pass-holders during Operation Bloodhound, Wildfire and Hydra.
Retired Collections do not drop at all making it impossible to acquire any of the skins from these collections except through trading or the Steam Community Market.
The Blacksite Collection was only available during the first few weeks of the launch of the Dangerzone game-mode.