While both of these terms are used to refer to a person who receives property from a loved one who has passed away (a decedent), the law actually treats them differently.
A beneficiary is a person or organization that receives money or property because someone specifically named them in their will or trust. The items being given could be things like money, property, or personal items like jewelry or a family heirloom. Beneficiaries can include any person, charity, or organization.
An heir is a relative who is entitled to money or property by law after someone dies if the decedent hadn’t chosen a beneficiary through an estate plan. For example, an heir could be a spouse, child, parent, etc. The word “heir” is often used when a person has died without a will or trust, so there’s no documentation indicating how the decedent’s property and money should be distributed. In this case, the estate administrator tries to find out who the rightful heirs are, and the Massachusetts laws of intestacy distribute assets to the appropriate heirs in a very specific way. Of course, a person can be both a beneficiary and an heir, like a child named in a will for example.