Yes. Basically when you play games you have a chance of a case being dropped to you and to open that case you need to buy a key from Valve themselves (or other players) which cost around $2.3, you can also buy cases from the market from other players they're very cheap usually like 0.03. Then you open them. The odds are however, absolute trash.
So basically a 0.25% chance of opening a knife and keep in minds some knives are only worth like 50 bucks so you'd need to be extremely lucky to profit off of opening cases.
Fun fact! There's an M4A4 skin called "Howl" which is discontinued due to some copyright bs which means none of those can be pumped into the game. When I started playing the game a few years back they were sitting around 100 bucks, now you'll be lucky to get one for 1000. Kind of like party hats and stuff in RS3 and people get banned with one from time to time so they disappear from the game as well.