A more thorough explanation:

An integrated contract is a final expression of one or more terms of an agreement. It can be one or more writings that fully express the intent of the parties, so that all earlier agreements are superseded. This means that neither party may later contradict or add to the contractual terms.

For example, if two companies sign an integrated contract for the sale of goods, the contract will contain all the terms of the agreement, and neither party can later claim that there were additional terms that were not included in the contract.

There are two types of integration: complete integration and partial integration. Complete integration is when the contract fully expresses the intent of the parties, and parol evidence (evidence outside the contract) is inadmissible. Partial integration is when the contract does not fully express the parties' intent, and parol evidence is admissible to clear up ambiguities with respect to the terms that are not integrated.

Another example of integration is in the context of wills and estates. When a testator combines more than one writing into a single document to form their last will and testament, it is called integration. The other writing must be present at the time of execution and intended to be included in the will.

Integration can also refer to the incorporation of different races into existing institutions, such as public schools, for the purpose of reversing the historical effects of racial discrimination. This is known as desegregation.

In the business context, integration can refer to a firm's acquisition of ownership of facilities that produce raw materials or parts for the firm's products. This is called backward integration. It can also refer to a firm's performance of a function that it could have obtained on the open market, such as entering a new market on its own, acquiring a firm that operates in a secondary market, or entering into a contract with a firm that operates in a secondary market. This is called vertical integration.

Finally, in securities law, integration refers to the requirement that all security offerings over a given period are to be considered a single offering for purposes of determining an exemption from registration. The Securities and Exchange Commission and the courts apply five criteria to determine whether two or more transactions are part of the same offering of securities.