A creature's saving throw gives it a chance to avoid being harmed when struck or shot. Most creatures have a saving throw based on what kind of armour they are wearing, so their saving throw may be improved if they are equipped with better armour. Other creatures, such as the reptilian Lizardmen, receive an armour saving throw for having scaly skin, while others may have a thick skin or chitinous shell which grants them an armour save.
Some troops are protected by magic or are incredibly tough by nature. These creatures have what is known as a Ward save, a special type of save which can save them from almost any type of damage.
Armour saves are taken by rolling a D6. If a creature has a 3+ armour save, it can normally avoid any wound it suffers by rolling 3 or more on a D6.