SMG: Short range, fully automatic, 40ish ammo, meant for close combat situations.
Assault Rifle: Mid-range, fully automatic, 30ish ammo, meant as all round weapon.
Burst Fire Rifle: 3 round-burst assault rifle. More accurate than AR but no option to go fully automatic. Used mostly at mid-to-far ranges.
Bolt-Action RIfle: Sniper Rifle. Long range, very high damage weapon, slow Rate of Fire. Single shot.
Combat Rifle: SIngle-shot rifle. Stronger than Assault Rifle, better range, less Rate of Fire. Mid-to-Long ranges.
LMGs: Machine guns. Good damage, inaccurate, lots of bullets, meant to throw lead downfield in large amounts. It's a machine gun.