Cover
Half cover: +2 AC/DEX saves. Three-quarters cover: +5 AC/DEX saves. Total cover: can't be directly targeted.
Walls, trees, creatures, and other obstacles can provide cover, making a target harder to hit.
Half Cover: An obstacle blocks at least half of a target's body (e.g., a low wall, thick furniture, another creature). Grants +2 to AC and Dexterity saving throws.
Three-Quarters Cover: About three-quarters of the target is blocked (e.g., an arrow slit, a thick tree trunk). Grants +5 to AC and Dexterity saving throws.
Total Cover: The target is completely concealed by an obstacle. A creature with total cover cannot be targeted directly by an attack or spell, though area effects can still reach around obstacles.
Determining cover: The DM decides whether a target has cover and from which direction. A creature has cover only if the obstacle is between the attacker and the target.
Creatures as cover: Other creatures (allies or enemies) between you and a target provide half cover to the target.
Spells and cover: Some spells specify that they require a clear path to the target and are blocked by total cover. Area spells that spread around corners can still affect creatures behind cover unless the spell description says otherwise.