The Capsule shop is a shop where players can try to win a special gun buy buying capsules.
The weapons are very good. They are much better (in some cases) then all of the normal shop guns.
Capsules usually contain normal items, but if it's the winning capsule then you win the gun that you wanted.
Each gun has a certain number of capsules remaining out of the total. Only 1 permanent gun can be won out of the 200.
Your chances get higher the less capsules are in there. If it's 2/200 You have half a chance of winning with 1 capsule.
Individiual capsules have a random chance of winning.