If the terms of a contract are clear and unambiguous, a court may not consider extrinsic evidence (any evidence not contained in the contract itself) when interpreting the document. This is known as:

Plain meaning rule

Explanation:

Plain meaning rule is a rule in statute or contract interpretation when the language is unambiguous and clear on its face the meaning of the statute or contract must be determined from the language of the statute or contract and not from extrinsic evidence.