Refers specifically to the position, rank, or status of the Japanese emperor. Often used in formal or historical contexts, such as discussions of succession or abdication.
His Majesty the Emperor succeeded to the imperial throne.
Discussions are being held regarding imperial succession.
The new emperor ascended the imperial throne.
The crown prince came to succeed to the imperial throne.
The emperor abdicated and passed on the imperial throne.
皇位 (the imperial throne) is a homophone of 高位 (high rank/status) but refers specifically to the emperor's throne, not general high rank.
Compound of 皇 (こう, 'emperor') and 位 (い, 'rank' or 'position'). The kanji 皇 is associated with the Japanese imperial line, and 位 denotes a formal status or seat.