Third party is referring to the person you injure if you were to be found negligent after an accident occurs. This is most commonly referred to as “liability” insurance on your policy and is expressed as “bodily injury & property damage” on your insurance declaration page under most circumstances. It may be abbreviated as “BI-PD” as a form of insurance shorthand. The limits may be expressed as a single limit for the “BI-PD” or as split limits shown as “BI” per person and per occurrence and “PD” per occurrence. Good luck.