Short answers, pulled from the story.
The Battle of Lützen was fought on the 2nd of May 1813 near the town of Lützen in Saxony. It was a major engagement of the War of the Sixth Coalition between Napoleon's French forces and a combined Prussian and Russian army.
The Allied army was commanded by Russian General Wittgenstein, who had been appointed commander-in-chief after Marshal Kutuzov fell gravely ill, and Prussian General Blücher. Blücher was wounded during the battle and command of the Prussian forces passed to General Yorck.
French forces lost 19,655 men in total, including 2,757 killed and 16,898 wounded, among them one of Napoleon's marshals. The Prussians lost at least 8,500 killed or wounded and the Russians lost 3,500 killed, wounded, or missing, though actual Russian casualties may have been higher.
The ferocity of both Lützen and the Battle of Bautzen eighteen days later, where Napoleon lost another 22,000 men, prompted him to accept a temporary armistice with Tsar Alexander and Frederick William III on the 4th of June 1813. Napoleon later regarded this truce as the undoing of his power in Germany.
The Lützen victory and the subsequent armistice encouraged Austria to join the Allied Coalition once the armistice expired. This shifted the balance of power dramatically against Napoleon and contributed to the broader collapse of French dominance in Central Europe.
Gerhard von Scharnhorst was described as one of the brightest and most able Prussian generals, serving as Wittgenstein's Chief of Staff during the battle. He was wounded at Lützen; although the wound itself was minor, the hasty Allied retreat prevented proper treatment and a fatal infection set in, costing Prussia one of its finest military minds.