Both heir and beneficiary are persons to whom property is passed in a probate situation.
Heir is known to many as one who inherits property from a deceased person, but don't forget that it refers to one who has not been mentined in the decedent's last will and testament.
The beneficiary is a person named in a will to get a share from the estate, either real or personal property.
To further confuse the situation, the beneficiary has other meanings, such as the person who uses the property of another for a certain period or for life.
