Perks are passive perks and include bonuses like running faster, increased bullet damage, and also extra Equipment or Lethal Equipment.
Perk Tier 1

C4 x2
Remote detonation explosive.
Unlocked: Default

Special Grenades x3
3 special grenades. No smoke.
Unlocked: Default

RPG-7 x2
Rocket Launcher with 2 rockets.
Unlocked: Default

Claymore x2
Trip activated explosives mine.
Unlocked: Level 23

Frag x3
3 Frag grenades.
Unlocked: Level 41

Bandolier
Extra ammunition magazines.
Unlocked: Level 32

Bomb Squad
Ability to seek out enemy explosives.
Unlocked: Level 14
Perk Tier 2

Stopping Power
Increased bullet damage.
Unlocked: Default

Juggernaut
Increased health.
Unlocked: Default

Sleight of Hand
Faster reloading.
Unlocked: Level 20

Double Tap
Increased rate of fire.
Unlocked: Level 29

Overkill
Carry two primary weapons, no pistol.
Unlocked: Level 38

UAV Jammer
Undetectable on enemy radar.
Unlocked: Level 11

Sonic Boom
Higher explosive weapon damage.
Unlocked: Default
Perk Tier 3

Extreme Conditioning
Spring for longer distances.
Unlocked: Default

Steady Aim
Increased hip-fire accuracy.
Unlocked: Default

Last Stand
Pull out your pistol before dying.
Unlocked: Level 8

Martyrdom
Drop a live Grenade when killed.
Unlocked: Level 17

Deep Impact
Deeper bullet penetration.
Unlocked: Default

Iron Lungs
Longer breath for steadier sniper shots.
Unlocked: Level 26

Dead Silence
Make less sound when you move.
Unlocked: Level 44

Eavesdrop
Hear voice chat of nearby enemies.
Unlocked: Level 35