Under the progress icon you can access the "Challenges" where there are various objectives which when completed and unlocked, allow you to add a badge, a mark, and a stripe to your display name, respectively, to be shown in lobbies and on the loading screen in-game.
There are numerous challenges for marks, badges, and stripes. These vary from killing enemies with specific weapons, to earning money, Crowns, and completing various other achievements.
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Kill 20 teammates with mines.
Kill 10 Heavy Gunners with Melee Weapons.
Perform 100 sliding headshots in PvP.
Kill 1000 jumping enemies.
Kill 1000 prone enemies.
Shoot the target above the bus, after shooting all six school bells.
Find the Rifleman duck in Pripyat.
Find the Medic duck in Pripyat.
Duck in the grass
Find the Engineer duck in Pripyat.
Duck and cover
Find the Sniper duck in Pripyat.
Take the 1st place in the winning team 50 times in Plant the Bomb.