Case opening sites are case simulators from the Counter Strike Global Offensive game. Cases on sites can either repeat similar games or have their own exclusive set of skins. Scrolling animation on websites can be either similar to the CS: GO game or different from it. The price of CS GO cases is very different from the prices in steam (including the key), so for many it is preferable to open cases on websites than in the game. Of course, there are differences, really rare and expensive skins, such as emerald / ruby / sapphire knives, can be knocked out exclusively from the cases in the game itself, it is impossible to get them on the sites (unless you are youtuber, of course).