Short answers, pulled from the story.
A prince-bishop was a Christian bishop who ruled a secular principality known as a prince-bishopric. This role originated in the 4th century when imperial power crumbled under barbarian invasions and bishops began making secular decisions for their communities.
Fifty-three ecclesiastical principalities comprised the Imperial states at the eve of the Protestant Reformation. The German Mediatization of 1803 secularized these territories following territorial losses to France in the Treaty of Lunéville.
The Holy Roman Empire dissolved in 1806 which caused the prince-bishop title to become defunct in the Confederation of the Rhine. Emperor Charles IV had previously confirmed the privileged status of Prince-Archbishoprics of Mainz, Cologne, and Trier through the Golden Bull of 1356.
The Prince Bishopric of Warmia was obtained by Poland following the Second Peace of Thorn in 1466. It ultimately abolished during Prussian annexation in 1772 during First Partition of Poland.
The Bishop of Urgell in Catalonia remains one of two co-princes of Andorra along with the French head of state currently its President. This unique arrangement persists where historical ecclesiastical authority meets modern political sovereignty in Pyrenees mountains despite all other bishops' princely titles being abolished by pope in 1951.