AR refers to parts or units that were removed from an aircraft and are now listed for sale. These could state a reason or occasionally be unrepairable after the product’s life.
OH - Overhauled
OH condition refers to the possible overhauling of the product or equipment. This could involve completely or partially disassembling the product and restoring it to an optimum/maximum level of functionality.
Certificates declared by seller
FAA Form 8130-3
Primary US airworthiness document. Confirms a part is new/repaired and fit for installation.
EASA Form 1
Primary EU/UK airworthiness document. EU equivalent of FAA 8130-3.
Certificate of Conformance
Confirmation of conformity to spec. Often for consumables.