A more thorough explanation:

A counterdeed is a type of secret deed that invalidates or alters a public deed. A deed is a written instrument that conveys an interest in property, usually land. A counterdeed is executed either before a notary or under a private seal.

For example, if a person sells a piece of land to another person through a public deed, but later regrets the sale, they may execute a counterdeed that invalidates the public deed and restores ownership of the land to the original owner.

Another example is if a person sells a piece of land to another person through a public deed, but later realizes that the public deed contains an error, they may execute a counterdeed that corrects the error.