An heir is who the law would give your property to if you did nothing - the people named by Arizona's intestate statutes, in the state's order. A beneficiary is who your documents actually name: in a will, a trust, or a designation on an account.
The two lists often differ, and when they do, documents beat defaults: a valid will overrides the intestate order, and a beneficiary designation overrides even the will. The estranged relative who is legally an heir inherits nothing if the documents say otherwise - and the dearest friend who is no heir at all inherits whatever the documents give.
Planning, in these terms, is simple: making sure the beneficiary list is current, complete, and identical to your intentions - so the heir list never gets consulted.
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Educational information only, not legal advice. Terms have statutory details beyond these summaries - confirm your situation with a licensed professional.