Walls, trees, creatures, and other obstacles can provide cover during combat, making a target more difficult to harm.
Half Cover. +2 bonus to AC and Dexterity saving throws. An obstacle blocks at least half of the target’s body.
Three-Quarters Cover. +5 bonus to AC and Dexterity saving throws. About three-quarters of the target is covered.
Full Cover. A target with full cover can’t be targeted directly by an attack or a spell.