Short answers, pulled from the story.
The Battle of Wagram was a two-day engagement on the 5th and the 6th of July 1809, part of the Napoleonic Wars. It ended in a French victory over the Austrian army under Archduke Charles, led to the breakup of the Fifth Coalition, and was at the time the largest battle in European history, involving around 300,000 men.
Austria believed the 1808-1809 political situation offered its best chance to recover provinces lost in 1805. Napoleon was bogged down in Spain, French forces in central Europe were reduced, and Austria hoped Prussia would join the fight, Germany would rise up, and Britain would land troops in the north. None of those conditions came to pass.
In late May 1809, Napoleon rushed a crossing of the Danube on fragile pontoon bridges. The main bridge broke during the fighting, cutting off reinforcements. The French were forced to retreat to Lobau island. The battle cost roughly 53,000 casualties and was Napoleon's first significant defeat.
Napoleon spent six weeks on Lobau island building hospitals for 20,000 wounded, warehouses, barracks, and a garrison. General Bertrand constructed two strong bridges to the island from the south bank starting on the 1st of June, protected by upstream palisades. A 124-gun battery was installed and patrol ships gave the French near-complete control of the Danube by the end of June.
Charles planned a double envelopment using his longer battle line, but coordination failed at every level. Two corps received their orders two hours late and could not reach their positions in time. Archduke John's 13,000-strong reinforcing army only began its march from Pressburg at 01:00 on the day of battle due to a delayed message. The attacks came piecemeal rather than simultaneously, allowing Napoleon to respond to each threat in turn.
The Treaty of Schonbrunn forced Austria to cede one sixth of its subjects and various territories, leaving the empire without a coastline until the German Campaign of 1813. Napoleon granted his chief of staff Berthier the hereditary title of 1st Prince of Wagram. Berthier had already held the title of Sovereign Prince of Neuchatel since 1806, and the new title allowed his descendants to carry the titles of Prince and Princess of Wagram.