Elemental Absorption is the capability of certain Anemo abilities to be infused with either Hydro, Pyro, Cyro, or Electro. Such abilities can only be infused once with a single element per use, and will deal damage of that type periodically throughout the ability's duration.
Absorption is not yet fully understood, and some of its details specifically around its inconsistency in triggering are still being investigated. A full list of sources which can act as triggers for Absorption has yet to be created.
So far it is understood that Anemo abilities with Absorption will always absorb from direct contact with:
Hydro, Pyro, Cyro, and Electro auras on objects, enemies, and players
Environmental effects that inflict the above elements
Hydro, Pyro, and Electro but not Cryo charged arrows
This means that it is insufficient to simply attack the Anemo ability with an elemental skill or infused weapon. If the skill has the capability to infuse the character with an absorbable element, then the character can then touch the ability to trigger absorption, or alternatively an enemy can be used as a carrier.
When there are multiple elements in range of the Anemo ability it will absorb according to elemental priority only. This priority is different between abilities and is either one of two orders:
Cryo > Pyro > Hydro > Electro
Anemo Traveler Skill
Anemo Traveler Burst
Pyro > Hydro > Electro > Cryo