What is an attachment that further describes the rights and duties of the parties in a contract?

An addendum serves as an attachment that provides additional details or clarifications about the rights and duties of the parties involved in a contract. It is often used to modify or supplement specific aspects of the original agreement without altering the entirety of the contract. This could include additional terms, definitions, or conditions that are relevant to the contract, allowing all parties to have a clearer understanding of their obligations and entitlements.

In contrast, other terms like contingency typically relate to conditions that must be met for the contract to be fully enforceable, while amendment focuses on formally changing an existing part of the contract. Consideration refers to the value exchanged between the parties as part of the agreement and does not pertain directly to the rights and duties as described in the question. Thus, the addendum aligns perfectly with the concept of providing further detail about the contract between the parties.