Regeneration

Summary
Regeneration (also known as healing factor) is a term given when a particular character can heal from wounds at an accelerated rate, even regenerating from wounds that would be lethal to normal humans. Regeneration has different levels.

Low levels of regeneration are essentially just faster natural healing, so a wound that could take weeks to heal would take days, hours, or even seconds. More advanced forms of regeneration can regrow lost limbs, organs, going all the way up to regenerating from decapitation, being blown to pieces or vaporized, and even complete physical destruction.

Types
Low: Faster healing ability for normal wounds. In machines and vehicles, this would be regenerating basic exterior damage.
 * Examples: Naruto Uzumaki (Naruto), Boy Blue (Vertigo Comics)

Mid-Low: Able to heal wounds that would normally leave large scars. In machines and vehicles, this would be regenerating damage that would normally leave large dents and openings.
 * Examples: Blade (Marvel Comics), Link (The Legend of Zelda), Roserade (Pokémon), Yusuke Urameshi (Yu Yu Hakusho)

High-Low: Able to regenerate some severed body parts like fingers, arms, and legs. In machines and vehicles, this would be regenerating some interior damage, and some minor critically damaged or destroyed parts.
 * Examples: Ulquiorra Cifer (Bleach), Wally West (DC Comics), Hercules (Marvel Comics)

Low-Mid: ''Able to regenerate limbs/fatal wounds. Still die from decapitation. In machines and vehicles, this would be regenerating minor parts and more extensive internal damage.''
 * Examples: Dante (Devil May Cry), Piccolo and other Namekians (Dragon Ball), Shirou Emiya with Avalon (Fate/stay night), Jason Voorhees (Friday the 13th), Wolverine (Marvel Comics)

Mid: Able to regenerate from decapitation. In machines and vehicles, this would be regenerating from the destruction of critical parts such as the engine.
 * Examples: Sakura Matou (Fate/stay night), The Hydra (Greek Mythology), Sayaka Miki (Puella Magi Madoka Magica)

High-Mid: Able to regenerate from being blown into pieces.
 * Examples: Meta-Cooler (Dragon Ball), Dio Brando (JoJo's Bizarre Adventure), Ryūko Matoi (Kill la Kill), Portgas D. Ace (One Piece)

Low-High: Able to regenerate from a puddle/drop of blood, or a small piece of your body.
 * Examples: Cell (Dragon Ball), Homunculi (Fullmetal Alchemist), Alucard (Hellsing), Ban (Nanatsu no Taizai), Deoxys (Pokémon)

Mid-High: Able to regenerate from being vaporized/dust.
 * Examples: Sosuke Aizen (Bleach), Majin Buu (Dragon Ball), Kirby (Kirby), Deadpool and Hulk (Marvel Comics)

High: Able to regenerate from a single molecule/atom/particle.
 * Examples: Anthrax (Bastard!!), Doctor Manhattan (DC Comics), The Sentry (Marvel Comics), Kakine Teitoku (To Aru Majutsu No Index)

Low-Godly: Able to regenerate as long as your disembodied consciousness exists, such as in the form of your soul or mind, or from other realms.
 * Examples: Dark Schneider (Bastard!!), Spawn (Image Comics), UlforceVeedramon (Digimon)

Mid-Godly: Able to regenerate even after every aspect of the mind, body, soul, and consciousness, are erased from existence.
 * Examples: Lavos (Chrono), Millenniummon and its other forms (Digimon), Sailor Moon (Sailor Moon), Chaos Gods (Warhammer)

High-Godly: Able to regenerate even if your existence is erased and the reality you are within is destroyed.
 * Examples: Crimson King (The Dark Tower), Swamp Thing (DC Comics), Yggdrasil (Digimon)

True Godly: Able to regenerate from being erased on a level beyond the confines and concept of dimensions themselves.
 * Examples: Characters from Touhou Project, Umineko, Demonbane, I/O, and the Masadaverse

(Credit to Versus Battles Wiki)