armor

[vazvaz]

Does armor reduces damage taken e.g. a swordsman that would have taken 10 damage from an archer with armor level 4 will only take 6?
Does cavalry -or any other unit- has "build in" armor (following the damage numbers in some battles it seems that cavalry has +1 armor than swordsmen), if the above definition of armor is correct.
Does forts get armor too?
Also where do area bonus/penalties apply? to the damage troops deal or to their health? how do armor or melee or archery levels are involved in the equation?