Short answers, pulled from the story.
The War of 1812 officially ended on the 17th of February 1815, when the United States Congress ratified the Treaty of Ghent. Peace terms had been agreed upon in December 1814, but the war did not formally conclude until congressional ratification.
The United States declared war primarily over British restrictions on American trade with Napoleonic France and the Royal Navy's practice of impressing sailors from American vessels, including men the United States considered American citizens. Tensions over British support for Indigenous confederacies resisting American expansion in the Old Northwest also contributed.
On the 24th of August 1814, British troops under Major General Robert Ross entered Washington after routing American militia at the Battle of Bladensburg. Ross ordered fire set to the White House and the United States Capitol. Valuable documents including the original Constitution had already been removed to Leesburg, Virginia, and the Navy Yard was burned by American forces to prevent its capture.
The Battle of New Orleans on the 8th of January 1815 was an American victory. A British expeditionary force of 8,000 troops under Major General Edward Pakenham attacked Andrew Jackson's fortifications south of the city and was repulsed with 291 dead, 1,262 wounded, and 484 captured or missing, compared to American official losses of 13 dead, 39 wounded, and 19 missing. The battle was fought after the Treaty of Ghent had already been signed.
The Castine Fund was 10,750 pounds in tariff duties collected by British forces during their occupation of Castine, Maine, which lasted from September 1814 until April 1815. When British forces withdrew, they took this money with them, and it was used to establish Dalhousie University in Halifax, Nova Scotia.
The Treaty of Ghent restored the pre-war territorial status quo but did not settle the core disputes that had triggered the war: impressment, neutral trade rights, and Britain's claimed maritime rights. Impressment largely ceased after 1815 because the end of the Napoleonic Wars removed Britain's wartime manpower need, but Britain did not formally renounce its broader maritime claims in the treaty.