A more thorough explanation:

Definition: Counter wills, also known as mutual or reciprocal wills, are separate legal documents created by two people that have identical or similar provisions leaving each person’s property to the other or to a third person. The agreement in a compact for mutual wills is that each person will dispose of his or her property in a certain way. The provision of each person leaving the other person their property is the consideration for the other. Counter wills are usually made between a married couple, and it is rare for them to execute a single counter will. It is also rare for counter wills to be made between more than two people.

Example: John and Jane are a married couple. They both create separate wills that leave all their property to each other. This means that if John dies, all his property will go to Jane, and if Jane dies, all her property will go to John. This is an example of a counter will.

Explanation: In this example, John and Jane have created separate wills that have identical provisions. They have agreed to leave all their property to each other, and this is the consideration for the other. If one of them dies, the other will inherit all their property. This is a common arrangement for married couples who want to ensure that their spouse is taken care of after they die.