Armoured fighting vehicle
Vickers Armstrong developed one of the first SPAAGs based on the chassis of the Mk.E 6-ton light tank/Dragon Medium Mark IV tractor, mounting a Vickers QF-1 "Pom-Pom" gun of 40 mm. The Germans fielded the Sd.Kfz. 10/4 and 6/2, cargo halftracks mounting single 20 mm or 37 mm AA guns (respectively) by the start of the war.

Self-propelled multiple rocket-launcher: Rocket launchers such as the Soviet Katyusha originated in the late 1930s. The Wehrmacht fielded self-propelled rocket artillery in World War II – the Panzerwerfer and Wurfrahmen 40 equipped half-track armoured fighting vehicles. Many modern multiple rocket launchers are self propelled by either truck or tank chassis.

Design: 

Survivability: The level of armour protection between AFVs varies greatly – a main battle tank will normally be designed to take hits from other tank guns and anti-tank missiles, whilst light reconnaissance vehicles are often only armoured "just in case". Whilst heavier armour provides better protection, it makes vehicles less mobile (for a given engine power), limits its air-transportability, increases cost, uses more fuel and may limit the places it can go – for example, many bridges may be unable to support the weight of a main battle tank. A trend toward composite armour is taking the place of steel – composites are stronger for a given weight, allowing the tank to be lighter for the same protection as steel armour, or better protected for the same weight. Armour is being supplemented with active protection systems on a number of vehicles, allowing the AFV to protect itself from incoming projectiles.

The level of protection also usually varies considerably throughout the individual vehicle too, depending on the role of the vehicle and the likely direction of attack. For example, a main battle tank will usually have the heaviest armour on the hull front and the turret, lighter armour on the sides of the hull and the thinnest armour on the top and bottom of the tank. Other vehicles – such as the MRAP family – may be primarily armoured against the threat from IEDs and so will have heavy, sloped armour on the bottom of the hull.

Firepower: Weaponry varies by a very wide degree between AFVs – lighter vehicles for infantry carrying, reconnaissance or specialist roles may have only a autocannon or machine gun (or no armament at all), whereas heavy self-propelled artillery will carry howitzers, mortars or rocket launchers. These weapons may be mounted on a pintle, affixed directly to the vehicle or placed in a turret or cupola.
The greater the recoil of the weapon on an AFV, the larger the turret ring needs to be. A larger turret ring necessitates a larger vehicle. To avoid listing to the side, turrets on amphibious vehicles are usually located at the centre of the vehicle.
Grenade launchers provide a versatile launch platform for a plethora of munitions including, smoke, phosphorus, tear gas, illumination, anti-personnel, infrared and radar-jamming rounds.
Turret stabilization is an important capability because it enables firing on the move and prevents crew fatigue.

Maneuverability: Modern AFVs have primarily used either petrol (gasoline) or diesel piston engines. More recently, gas turbines have been used. Most early AFVs used petrol engines, as they offer a good power-to-weight ratio. However, they fell out of favour during World War II due to the flammability of the fuel.
Most current AFVs are powered by a diesel engine; modern technology, including the use of turbo-charging, helps to overcome the lower power-to-weight ratio of diesel engines compared to petrol.
Gas turbine (turboshaft) engines offer a very high power-to-weight ratio and were starting to find favour in the late 20th century – however, they offer very poor fuel consumption and as such some armies are switching from gas turbines back to diesel engines (i.e. the Russian T-80 used a gas turbine engine, whereas the later T-90 does not). The US M1 Abrams is a notable example of a gas turbine powered tank.

Modern classification by type and role: Notable armoured fighting vehicles extending from post-World War I to today.

Tank: The tank is an all terrain AFV incorporating artillery which is designed to fill almost all battlefield roles and to engage enemy forces by the use of direct fire in the frontal assault role. Though several configurations have been tried, particularly in the early experimental "golden days" of tank development, a standard, mature design configuration has since emerged to a generally accepted pattern. This features a main tank gun or artillery gun, mounted in a fully rotating turret atop a tracked automotive hull, with various additional secondary weapon systems throughout.
Philosophically, the tank is, by its very nature, an offensive weapon. Being a protective encasement with at least one gun position, it is essentially a pillbox or small fortress (though these are static fortifications of a purely defensive nature) that can move toward the enemy – hence its offensive utility. Psychologically, the tank is a force multiplier that has a positive morale effect on the infantry it accompanies. It also instills fear in the opposing force who can often hear and even feel their arrival.

Tank classifications: Tanks were classified either by size or by role.

		
			
			
		
		
			
			
		
		
			
			
		
		
			
			
		

Classification by relative size was common, as this also tended to influence the tanks' role.

Light tanks are smaller tanks with thinner armour and lower-powered guns, allowing for better tactical mobility and ease of strategic transport. These are intended for armoured reconnaissance, skirmishing, artillery observation, expeditionary warfare and supplementing airborne or naval landings. Light tanks are typically cheaper to build and maintain, but fare poorly against heavier tanks. They may be held in reserve for exploiting any breakthroughs in enemy lines, with the goal of disrupting communications and supply lines.
Medium tanks are mid-sized tanks with adequate armour and guns, and fair mobility, allowing for a balance of fighting abilities, mobility, cost-effectiveness, and transportability. Medium tanks are effective in groups when used against enemy tanks.
Heavy tanks are larger tanks with thick armour and more powerful guns, but less mobile and more difficult to transport. They were intended to be more than a match for typical enemy medium tanks, easily penetrating their armour while being much less susceptible to their attacks. Heavy tanks cost more to both build and maintain, and their heavy armour proved most effective when deployed in support infantry assaulting entrenched fortifications.
Over time, tanks tended to be designed with heavier armour and weapons, increasing the weight of all tanks, so these classifications are relative to the average for the nation's tanks for any given period. An older tank design might be reclassified over time, such as a tank being first deployed as a medium tank, but in later years relegated to light tank roles.
Tanks were also classified by roles that were independent of size, such as cavalry tank, cruiser tank, fast tank, infantry tank, "assault" tank, or "breakthrough" tank. Military theorists initially tended to assign tanks to traditional military infantry, cavalry, and artillery roles, but later developed more specialized roles unique to tanks.
In modern use, the heavy tank has fallen out of favour, being supplanted by more heavily armed and armoured descendant of the medium tanks – the universal main battle tank. The light tank has, in many armies, lost favour to cheaper, faster, lighter armoured cars; however, light tanks (or similar vehicles with other names) are still in service with a number of forces as reconnaissance vehicles, most notably the Russian Marines with the PT-76, the British Army with the Scimitar, and the Chinese Army with the Type 63.

Main battle tank: Modern main battle tanks or "universal tanks" incorporate recent advances in automotive, artillery, armour, and electronic technology to combine the best characteristics of the historic medium and heavy tanks into a single, all-around type. They are also the most expensive to mass-produce. A main battle tank is distinguished by its high level of firepower, mobility and armour protection relative to other vehicles of its era. It can cross comparatively rough terrain at high speeds, but its heavy dependency on fuel, maintenance, and ammunition makes it logistically demanding. It has the heaviest armour of any AFVs on the battlefield, and carries a powerful precision-guided munition weapon systems that may be able to engage a wide variety of both ground targets and air targets. Despite significant advances in anti-tank warfare, it still remains the most versatile and fearsome land-based weapon-systems of the 21st-century, valued for its shock action and high survivability.

Tankette: A tankette is a tracked armed and armoured vehicle resembling a small "ultra-light tank" or "super-light tank" roughly the size of a car, mainly intended for light infantry support or scouting. Tankettes were introduced in the mid-1920s as a reconnaissance vehicle and a mobile machine gun position They were one or two-man vehicles armed with a machine gun. Colloquially it may also simply mean a "small tank".
Tankettes were designed and built by several nations between the 1920s and 1940s following the British Carden Loyd tankette which was a successful implementation of "one man tank" ideas from Giffard Le Quesne Martel, a British Army engineer. They were very popular with smaller countries. Some saw some combat (with limited success) in World War II. However, the vulnerability of their light armour eventually caused the concept to be abandoned.