The Division is not an MMO like most people believe. It is in fact an Online - Open World - RPG which seems the same but with some slight differences (1 of them being that you don't have to pay a monthly fee like all the MMO out there). You can play both alone and with 3 other players in co-op while on the main campaign against NPC's. You can encounter other players and add 1+ player to your squad as the drone with the companion app, on areas such as PVP and or social zones. Despite the fact it will be always online, you can still play alone and not go into the PVP or Social Zones.
Ubisoft will be launching an official Rainbow Six Siege Marketplace soon, where players will be able to buy and sell skins between each other
Here's a breakdown of everything coming to Rainbow Six Siege Y8S4, including its newest operator, map, balancing changes, and more!