A Trustee is the person or institution responsible for managing the assets placed in a Trust. They’re appointed by the person who creates the Trust (called the Grantor) and are legally required to follow the instructions in the Trust document.
In many cases—especially with a revocable living trust—the Grantor serves as the initial Trustee, keeping full control over their assets. They also name a Successor Trustee to take over if they become incapacitated or pass away.