The Wikipedia page for the Schmalkaldic War list the Duchy of Saxony and the Electorate of Saxony as opposing sides of the war, each with their own monarch (Maurice is the Duke of Saxony, John Frederick I is the Elector). From reading the rest of the page, looks like John Frederick I is the main leader of Saxony. What was the Duchy of Saxony then? Was it a subordinate territory to the Electorate? Or was it a different land, ruled independently from the Electorate? Or was it just a title, like the "Prince of Wales" in the UK does not really rule Wales? How did it come to be separate from the Electorate?
Another curious thing is that in the succession box below their articles, Wikipedia claims that after the Elector's defeat, they exchanged their title (Maurice became Elector, JF became Duke). Why did they grant the Duke title to the defeated Elector?