Short answers, pulled from the story.
The Panther-Wotan line, also called the Ostwall or Eastern Wall, was a German Wehrmacht defensive line on the Eastern Front built between 1943 and 1944. It stretched from Narva on the Baltic Sea in the north to the Sea of Azov in the south, running largely along the Dnieper river. It was only partially completed before the Red Army broke through in mid-1944.
Adolf Hitler rejected early proposals for the line, advanced by Erich von Manstein among others, primarily for political reasons. He argued that a developed defensive line would tempt soldiers to retreat from the actual front. He relented only in August 1943, after the Battle of Kursk made it clear the Wehrmacht could no longer conduct offensive operations in the east.
Construction began on the 8th of September 1943, relying on tens of thousands of civilian workers to build bunkers, anti-tank trenches, and barbed wire barriers. Army Group South was already falling back toward the unfinished line by the 15th of September 1943.
Between the 26th of September and the 20th of December 1943, the 2nd, 3rd, and 4th Ukrainian Fronts suffered 173,201 unrecoverable losses and 581,191 sick and wounded, totaling 754,392 casualties. These losses came during the Lower Dnieper strategic offensive operation aimed at breaking through the line.
The two segments were divided at the Zaporozhe bridgehead on the Dnieper. The Panther Line ran north of the bridgehead along the western bank of the Dnieper toward the Baltic, while the Wotan Line ran south of the bridgehead east of the Dnieper down to Melitopol and the Sea of Azov. The Wotan Line was placed east of the river to prevent the isolation of the Crimea.
Georg von Küchler, commander of Army Group North, refused to use the name Panther Line because he feared it would give his soldiers false confidence in the line's strength. Construction had barely started when troops were already falling back onto it, and he did not want the name to suggest a level of protection the fortifications had not yet achieved.