There are generally four different parties named in a Living Trust document.
Trustor (Grantor, Settler, Donor) - the individual or couple that establishes the Trust.
Trustee - the person named by the Trust as the controller of the Trust's assets; responsible for managing the property that is titled in the name of the Trust. Often, the Grantor names him/herself as the Trustee.
Beneficiary - an heir that will receive the property held in Trust once the Grantor has died.
Successor Trustee - If the Grantor has named him/herself as the Trustee, the Successor Trustee is responsible for taking care of the estate assets and distributing them to named Beneficiaries after the Grantor's death. A Successor Trustee is also often named in case the first choice for Trustee cannot fulfill his/her duties for some reason.
Estate planning - fundamentals of Trusts and Living Trusts. (n.d.-a). https://www.hg.org/trusts-and-living-trusts.html