Mystery box
A box sold at a fixed price that reveals one item at random from a published list of items and odds.
A mystery box is sold at a fixed price and holds one item drawn at random from a list shown on the box page, usually with the odds for each item. Physical-prize sites ship the item or let you exchange it for balance; CS2 case sites pay out in skins.
To judge a box, multiply each item value by its odds and add them. The gap between that expected value and the price is the site's edge.