Campfires can be found throughout the game. They are rest zones where you can use Invocation. When standing inside the radius, your health regenerates faster, though this will not work when in battle stance (thus, fighting next to a fire to auto-heal is not possible). They also act as a safe point. When you die, you are usually sent back to the last Campfire you stood in.
While Campfires are permanently fixed to a spot, there exists also a consumable item which is equivalent, allowing you to use most of a campfire's functions while travelling: the Portable Altar. This lets you use most of the Campfire's features, except it does not act as a safe point.