Unlike most other elemental reactions, Burning targets will have both a Pyro and a Dendro aura simultaneously and requires both auras to work. If a unit is affected by Pyro and takes Dendro damage but the source of the damage does not apply a Dendro aura, then the Burning reaction will occur but have no effect due to there being no Dendro aura.
Note that in the open world, grass, haystacks, shrubs, small trees, crates, and barrels are all Dendro objects. Using Pyro abilities on them will ignite them as well as the surrounding area. After being burnt, grass will be charred and cannot be burned again until the area resets, while shrubs and trees will be temporarily destroyed. Units that are Burning will also spread fire to combustible objects that they touch such as grass.
Currently, players can only burn if they are inflicted with Dendro from a Dendro Samachurl or a poison status from a Large Dendro Slime and Pyro from another source. Burning damage caused this way scales with the active character's own Elemental Mastery. This damage is separate from the damage taken when standing on burning grass without being affected by Dendro.
The amount of Pyro damage dealt by a fire depends on the player's World Level. At its minimum, Burning deals 2 Pyro DMG every half second, and at its maximum, fire deals 100 Pyro DMG every half second. If a Dendro construct like grass is set on fire, it will extinguish after the status expires or once it comes into contact with Electro, Cryo, or Hydro.