Some people are confused with the differences between executor and trustee, probably because they seem to be the same. It is true that they both have to make sure that they need to choose the right beneficiaries for their trust or estate. The things that they have to do are quite different, though.
The executor is going to act more like a liquidator while the trustee is going to work more as a business manager so that things can be worked out properly. Remember that the trustee can sometimes be appointed by the person who has created the trust. This is somewhat similar to a person choosing a personal representative for the estate that he has.