an elevated seat of honor: the chair that marks who holds authority, above all a king's throne
At its root the word names a raised seat, the kind you would not sit in casually. From there it almost always carries the weight of office: the one seated on it holds power, and the seat itself comes to stand for that power. A throne is rarely just furniture in the Hebrew Bible; it is shorthand for a reign, a dynasty, the right to rule.
The three shades below are one idea seen from different chairs. A plain seat in a room, the throne of a human king, and the throne of God all share the same picture: someone is seated high, and that seating signals who is in charge. Because the seat stands for the rule, the writers can speak of a throne being established, overturned, inherited, or made secure, and mean the kingdom itself.
The royal sense dominates, and within it the recurring phrase is the throne of David: not the literal chair but the promise that David's line would keep the kingship. The highest use lifts the same word to God, whose throne is fixed in the heavens and founded on justice. The reader should hear continuity, not three unrelated objects: the lowly chair and the throne of heaven are the same word because they are the same gesture of authority, scaled up.