One of the defining characteristics of "Call of Duty" multiplayer is the concept of "perks." The concept isn't anything new to games: Think of perks like a temporary power-up.
In the case of Blackout, you pick up various types of perk — Brawler, or Looter, or Medic, or a variety of others — and they offer temporary ... perks.
In the case of Looter, for example, you're able to see the outline of any loot near your character. That's tremendously helpful, as you can scan a building's loot from the outside instead of running in and sifting through it all yourself. You may also notice that loot is slowly disappearing from the house you're looking at — likely because someone is grabbing it quietly. And now you've got the jump on them!
A well-timed perk use in Blackout can mean the difference between life and death, and it's a brilliant new twist to the Battle Royale formula.