A more thorough explanation:

A testamentary trust is a type of trust that is created in a person's will. It only comes into effect after the person has passed away.

For example, let's say that John creates a will that includes a testamentary trust for his daughter, Sarah. John passes away, and the trust is then established for Sarah's benefit. The trust will be managed by a trustee, who will be responsible for distributing the assets in the trust to Sarah according to the terms of the trust.

Another example could be a person who wants to leave money to a charity after they pass away. They could create a testamentary trust in their will that specifies how the money should be used by the charity.

Overall, a testamentary trust is a way for a person to ensure that their assets are distributed according to their wishes after they pass away. It can be a useful tool for estate planning and can provide peace of mind for the person creating the trust.