Sometimes, you need an edge. Scorestreaks reward your performance by allowing you to call in support from outside the battlefield, whether it’s equipment, cover fire, AI backup, or a bombing run.
You can set any three Scorestreaks before entering a match, which automatically arrange themselves in ascending order of their cost. Your progress towards your Scorestreaks is reset to zero if you die. You can hedge that bet with certain types of Basic Training but, in general, the system rewards conservative and skillful play.
It’s important to note here, especially for newcomers, that the points you earn towards a Scorestreak are not consumed when the Scorestreak is used. You aren’t paying for the Scorestreak out of a pool of accumulated points; instead, you’re just unlocking it. If you use a cheap Scorestreak early on, you aren’t harming your progress towards the more expensive ones.
Most of the Scorestreaks are not intended to be equally useful in all situations. Call of Duty’s maps and modes are designed to encourage players to be flexible and adjust their loadouts as required for their current game. You should tailor your approach accordingly, switching out your Scorestreaks as required for your skill level, character build, and current game type. If you know you’re going to spend a lot of time in close-quarters combat, for example, that’s when you want to pick a Flamethrower.