How does armor work?

[Mithrandale]

I just finished reading through everything in the Age of Empires wikis about armor and I think I understand less now than when I started! It seems to me that the wikis are written for people who understand the underlying code and not just for regular players (kind of like Microsoft Help where in order to understand the help you have to know enough that you don't need the Help).
I want to use the "Change Object Armor" trigger to buff some units to make a tougher bodyguard group for a hero,but I have no idea what the values are or how they work. I also want to buff up all markets so when I attack a civ the market is hard to kill so I can keep it there and run trade caravans to it.
So is armor a small integer value, or bigger? Like if I add 5 to a unit's armor, is that a big change or an insignificant one?

[Heimdall313]

+5 armor is a big change, yeah.
Armor and Attack are simple, low value integers. If your unit has 17 attack (fully upgraded Champion is 13+4 as an example) and attacks another unit with 5 points of armor (Elite Berserk, 2+3), he does 12 damage (17-5).
There's hidden bonuses that complicate things of course (Byzantine Cataphracts being the staple example), such as bonus damage and bonus defense. That's how Skirmishers, Pikemen, etc. work as counter units.

Elite berserks are pretty tough infantry units: 72 HP, 18 Atk, 5 Def, 5 Pierce Def. Adding +5 def to your hero, assuming he's got stats like an Elite Berserk, is a big buff. Elite Teutonic Knights are the bulkiest Infantry in the game, with 100 HP, 21 Atk, 13 Armor, 6 Pierce Armor.
Assuming you have a Champion attacking both, the Berserk drops in 6 hits (actually 7, counting HP regen) and the Teutonic Knight takes 25 hits. Raise that berserk to 10 Def, and its 11 hits to drop (12 with regen).

Not sure how to run the triggers; don't use them much.
Market, set your diplomacy Neutral and your units won't attack it unless directly ordered.

[jonoliveira12]

Armour reduces attack daage of the specified type (Melee or Pierce), by the sum amount, but never less than 1 damage.
It also does not offer any protection from Bonus Damage values.

Example:

-Unit A deals 6 melee damage + 5 bonus damage to unit B.
-Unit B has 7 melee armour and 2 pierce armour.
-Unit C has 5 melee armour and 0 pierce armour.

-Upon attack, Unit A deals 6 damage to Unit B (6 melee damage against 7 melee armour, because damage can never be less than 1, amounts to 1 damage, + the 5 bonus damage it has against Unit B).
-Upon attack, Unit A deals 1 damage to Unit C (6 melee damage - 5 melee armour = 1 damage).

I hope this helps.

[DesertRose92]

For a very throughout explanation of how things work:
https://www.youtube.com/watch?t=223&v=goGhuZA7Jvs&feature=youtu.be

[DMg Halt]

Make a trigger, and create an effect 'change object armor'

We'll use a spearman for the example

Set object to spearman

Change the operation to "Set"

Type in your desired Quantity (we'll use 69)

Set Armor/Attack Type to ZERO

Test the scenario, your unit should now have 0+69/0+69 armor.

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Here is a link that might be helpful.

https://ugc.aoe2.rocks/general/damage_calculation/#32-list-of-damage-classes

If you scroll down to the list of Damage Classes, it says Base Pierce = 3, and Base Melee = 4.

So if you typed 4 in the Armor/Attack type instead of ZERO, your unit would have
0+69/0 armor. If you typed 3, it would be 0/0+69, understand?