The term “third (3rd) party” is used to refer to a neutral actor who is not interested in the outcome of an interaction taking place between two parties. A Third party is introduced into events in order to mediate the activity taking place and be the resolving party in any emergency events.
One party is willing to pay another party is they harvest 10 tons of wheat for them. The party that is harvesting is worried that if they do what they promised and send over the wheat, that the other party might not pay. Likewise, the Party who requested the harvesting is worried that perhaps the harvesters will do a bad job or steal some of the harvests. So, they introduce a neutral third party to oversee that both parties hold up their ends of the agreement.