How damage works
Every attack and harmful spell deals a damage type. The type does nothing on its own, but some creatures and items grant resistance, vulnerability or immunity to certain types.
Resistance halves damage of that type (rounded down), vulnerability doubles it and immunity means you take none. Multiple instances of resistance to the same type count as one.
Acid
Corrosive liquids and digestive enzymes, like a black dragon's breath or an acid arrow.
Example spells: Acid Arrow, Acid Splash
Bludgeoning
Blunt force: hammers, falling, constriction and rolling boulders.
Example spells: Wind Wall
Cold
Freezing cold: icy rays, winter winds and a white dragon's breath.
Example spells: Ray of Frost
Fire
Flames and searing heat: fireballs, torches and a red dragon's breath.
Example spells: Burning Hands, Fire Bolt, Fireball, Flaming Sphere, Heat Metal, Hellish Rebuke, Produce Flame, Scorching Ray
Force
Pure magical energy. Few creatures resist it.
Example spells: Eldritch Blast, Hunter's Mark, Meld into Stone
Lightning
Electricity: lightning bolts, shocking spells and a blue dragon's breath.
Example spells: Call Lightning, Lightning Bolt, Shocking Grasp
Necrotic
Life-draining death energy, the weapon of the undead and dark magic.
Example spells: Bestow Curse, Chill Touch, Hex, Inflict Wounds, Vampiric Touch
Piercing
Puncturing attacks: spears, arrows and monster bites.
Example spells: Ensnaring Strike, Ice Knife, Spike Growth
Poison
Venomous stings, toxic gas and a green dragon's breath.
Example spells: Poison Spray, Ray of Sickness
Psychic
Mental assaults: mind-rending powers and terrifying visions.
Example spells: Dissonant Whispers, Mind Spike, Phantasmal Force, Vicious Mockery
Radiant
Holy light and celestial fire, the power of clerics and angels.
Example spells: Divine Favor, Divine Smite, Guiding Bolt, Moonbeam, Sacred Flame, Shining Smite, Spirit Guardians, Starry Wisp
Slashing
Cutting attacks: swords, axes and claws.
Example spells: Conjure Animals
Thunder
Concussive sound: thunder and shockwave spells.
Example spells: Shatter, Thunderwave