Senjou de Shoujo wa Kokoro wo Sagasu/Unit types

Infantry
The infantry is generally speaking the weakest in terms of offense and defense. It's main advantages is its ability to occupy installations to turn them into supply stations for your own troops.

Armored vehicle
Armored vehicles have high evasion and high movement, and can run right past the enemy, which makes them good at flanking or directly hitting the back line.

Tank
Tanks are sturdy and powerful.

Self-propelled artillery
Artillery units are perhaps the most powerful of all unit types, combining long range with heavy firepower. However, it has extremely weak armor which can get it killed in just one or two hits. It also can't attack units immediately adjacent to it. Finally, it cannot attack immediately after it moves.

Note: There's a bug in earlier versions of the game where the MLRS can in fact attack after moving. This bug has been fixed in the version 2.01 patch.

Anti-Air units
One of the few unit types that can attack air units. They are sub-divided into anti-aircraft guns and anti-air missiles. Anti-aircraft guns can attack both air and ground units, though its power against ground units is very weak. Anti-air missiles can only attack air targets, not ground units, and it cannot attack right after moving. On the plus side, the missiles have long range.

Fighter planes
Fighter planes can attack both air and ground units, although it's significantly stronger at blasting ground targets. It can only be resupplied at airports.

Helicopters
Helicopters can only attack ground units. They may be resupplied at any buildings, not limited to just airports.