The Parol Evidence Rule generally prohibits the use of extrinsic evidence to alter or contradict the terms of a written contract, but exceptions exist where such evidence is necessary to clarify ambiguities, prove fraud, mistake, or duress, or to demonstrate that the written contract was not intended to be a complete and final representation of the parties' agreement. These exceptions ensure that justice is served by allowing relevant evidence to be considered in specific circumstances where the written document does not fully capture the parties' intentions or where there are legal defects in the contract formation process.