While both an executor and trustee deal with estates, make sure beneficiaries get their inheritances, and pay taxes and debts, they’re very different roles.
An executor of estate deals with an estate after the owner is deceased. A trustee takes care of a trust as long as the trust is in existence—which can be during the life of the trust creator and/or after they are deceased. Trusts can last a very long time, so a trustee’s responsibilities are usually a lot bigger than an executor’s.