Trustor, grantor, settlor and donor can all be used interchangeably and refer to the person(s) who is/are crating the trust.
Trustee is the person who is designated to act on behalf of the trust.
Beneficiary is the person for whose benefit the trustee is supposed to act.
In short, once the trust is created by a trustor and funded with is/her assets, it is a separate entity that owns those assets. The trustee is the only person who can manage those assets and has to do so in the best interest of the beneficiary.
Oftentimes, though, Trustor, Trustee and Beneficiary can be the same person until his/her death. Then a Sucessor Trustee takes over the management of the trust assets for the other beneficiaries identified in the trust document.
Hope this helps!
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Opinions are my own.
"I was gratified to be able to answer promptly. I said I don't know." - Mark Twain