Damage

Damage is a measurement of how harmful an attack is to a character. When a character takes Damage, it is subtracted from their Hit Points. Damage will cause death when a character's hit points reach 0.

Influences
Weapons all have base damage values. The final damage delivered to the target, can be possibly modified by various factors, depending on the game:

Fallout: New Vegas features a few weapons that completely ignore DR, even if few enemies actually have DR.

Damage done to the player in V.A.T.S. is reduced by 90%.

Damage done to the player in V.A.T.S. is reduced by 25%. Melee/unarmed damage done by the player is doubled.

Damage done to the player in V.A.T.S. is reduced.

Weapons cannot be equipped when their durability reaches 0.

Chance to avoid 100% of incoming damage. Used only by the Serendipity perk.

Incoming damage is reduced by a percentage. Occurs after damage resistance calculation.

Reduces the target's damage resistance value, and calculates damage based off of that lowered value.

Only used in Fallout 76 PVP. An end-of-calculation limit on how much maximum damage can be dealt per hit marker to another player. This value is 110.

Types
There are different types of damage, depending on the weapon of attack:

Not shown in the games that use it, Electrical damage is only caused by alien blaster, YK32 pulse pistol, and YK42B pulse rifle.

Fallout 3 and Fallout: New Vegas use "energy" damage to label the residual effect off the Tesla cannon, though it has the appearance of electricity sparking.

All Fallout games contain environmental radiation damage of some variant. The table is representative of radioactive damage dealt by weapons like the gamma gun.

Exists in the game files, but is not used anywhere.

Also known as physical damage in Fallout 76.

In Fallout 76, it is used only by the Electrically Charged mutation, but calculates using energy resistance. This effectively makes it energy damage, but grants special immunity to certain effect interactions.

In Fallout 4 and 76, explosive is not its own damage type, rather it is a damage sub-type. Explosives are a way to deal proper damage types. For example, a missile launcher will create an explosion that deals physical damage, while a plasma grenade will create an explosive that deals both physical and energy damage.

In Fallout 4 and 76, bleed damage is not its own damage type, rather it is a damage sub-type. Bleed damage will deal physical damage, but is exempt from being reduced by damage resistance.

Special exceptions

 * Fallout Tactics adds Gas Damage. It also re-categorizes "Laser" as "Energy" damage.
 * Van Buren adds Ballistic, Bio, and Heat damage.