The AK-74--Russian: Автомат Калашникова образца 1974 года or "Kalashnikov Automatic Rifle Model 1974"--is a 5.45mm assault rifle developed in the early 1970s in the Soviet Union. Refined version of the AK-47 and introduced in 1974.
First saw service with Soviet forces engaged in the Afghanistan conflict and continues to be used by the majority of countries of the former USSR.

The successor to the AK-47. It is currently employed by the Russian armed forces. The bullet caliber is 5.45X39mm. The bullet has a higher muzzle velocity than the old 47's 7.62X39mm. The 74 is more accurate than its predecessor, with an effective range of around 540 yards. Mikhail Kalashnikov created this gun at the behest of the Soviet Military in response to the 5.56X54mm round fielded by the M-16. This was done to keep up with the Americans more than anything else, and Mister Kalashnikov himself opposed the new gun. The new bullet is standard military FMJ, but a hollow space in the tip enables the bullet to quickly tumble within two inches of penetration, resulting in horrible wounding. The weapon is as reliable than the
AK-47, substantially more accurate, lighter, and the ammunition doesn't weigh anywhere near as much. As far as cold war assault rifles go, this is about as close to god's own anti-son-of-a-bitch machine that you can get.

The gun which replaced the akm (upgraded ak-47) in the mid 70's in the soviet armed forces.
Cartridge: 5.45x39mm
Rate of fire: 600 rounds per minute
Fire modes: safe-semi auto-full auto
Action: long stroke gas piston
The 5.45x39 is much faster and more accurate then the ak-47 7.62x39. The ak-74 also has a muzzle brake which allows it to have the lease amount of recoil of any assualt rifle.
The ak-74 is more reliable then the ak-47 because it has a bigger shell extractor.
A little know fact about the 5.45x39 is that it still has quite a bit of stopping power. When the 5.45x39 hits anything it immidiatly flips around, leaving a nasty wide hole in the target. This is quite unlike the m-16's 5.56x45 and the ak-47's 7.62x39 rounds as they just pencil right thru flesh leaving a small hole.

The ak-74 has been used by the russians since 1990 in the form of the ak-74m.

Other varients:

U=shortened S=folding stock
aks-74: folding stock varient
aks-74u Krinkov: folding stock and short barrel
ak-74m: current issue russian rifle, polymer furniture instead of wood and has a folding stock
ak-74u- a varient that is only found in video games, if this gun did exist then it would have a short barrel but no folding stock.
The ak-74 is a rifle not a submachine gun

A way to tell the ak-74 and the ak-47 apart is that the ak-74 has an almost straight magazine and the ak-47 mag is shaped like a bannana

Kalashnikov designed weapon, reformed from the AK-47. It is the main stay of the Russian Infantry. It has a 5.45 x 39mm bullet. More like the 5.56mm which the American M-16A2 uses. It is much more accurate and more muzzle velocity. Simple terms, a very much improved AK-47.
Calibur-5.45 x 39mm
Weight-3.3kg unloaded 3.9 loaded
Barrel-415mm
Rate of Fire-600-650 rds/min
Operation-Gas
Length-943mm
Rifling-4 grooves rh, 1 turn in 196mm
Muzzle velocity-900m/s
Effective range-500m (50 short of M-16a2)

A Russian assault rifle first produced in 1974, hence the name AK-74. Basically a refined AK-47 made to fire the 5.45x39mm, an obviouis nod to the NATO 5.56x45 round. Has one variant, the AK-74u.

A Russian assault rifle, designed by Kalishnakov, in response to the NATO 5.56x45mm round. Instead of the AK-47's 7.62x39mm round, it uses a bottle-necked 5.45x39mm round. It has many variations like the AK-47, including the ultra-short AK-74SU, developed for Russian special forces and tank crews.

A gun frequently used by Pakis but the Russians made it

A variant of the most popular rifle built by the legendary Mikhail Kalashnikov.
The AK-74 is basically an AK chambered for the 5.45x39mm round, which is supposed to be similar to the 5.56x45mm NATO round that America and its allies use in their assault rifles (such as the M16 series and M4 carbine); as opposed to the AK-47 being chambered in the 7.62x39mm round. Reports indicate that this rifle is less accurate than the M16, but because the AK-74 doesn't have so many inner moving parts, it is easy to disassemble and maintain.

On another note, the AK-74, like its cousin '47, is a commonly blackmarketted weapon by various terrorist factions, mostly in third world nations like Arabia.

It's not an AK-47. That's all you need to know.