Short answers, pulled from the story.
A battleship is a large, heavily armored warship with a main battery of large-caliber guns, designed to serve as a capital ship. It differed from other warships in its combination of heavy armor protection and powerful main armament, which allowed it to engage and destroy enemy battleships while withstanding return fire.
HMS Dreadnought, ordered by Admiral Sir John Fisher, was the first all-big-gun battleship to be completed. She carried ten 12-inch guns in twin turrets and abandoned the medium-caliber secondary battery entirely. Her launch rendered every existing battleship obsolete and triggered a worldwide naval arms race, with "dreadnought" becoming the generic term for any modern battleship.
The Battle of Jutland, fought on the 31st of May - the 1st of June 1916, was the largest clash of battleship fleets in history. Three British battlecruisers and one German battlecruiser were destroyed, but the German High Seas Fleet escaped under cover of darkness and neither side achieved a decisive result. The battle confirmed that a full fleet engagement would likely favor Britain, leading Germany to abandon battleship tactics and turn to unrestricted submarine warfare.
The Washington Naval Treaty of 1922, signed by the United States, United Kingdom, Japan, Italy, and France, imposed a ten-year building holiday on new battleships and fixed a displacement ratio of 5:5:3 for the US, UK, and Japan respectively. The treaty also severed the Anglo-Japanese Alliance. Fewer battleships were built in 1919-1939 than in 1905-1914 as a direct result of the treaty limitations.
Aircraft displaced battleships during World War II. The Battle of Taranto in November 1940, the attack on Pearl Harbor on the 7th of December 1941, and the sinking of HMS Prince of Wales and HMS Repulse on the 10th of December 1941 all demonstrated the new reality. The sinking of Prince of Wales and Repulse was the first occasion aircraft had sunk capital ships that were maneuvering and returning fire.
All four Iowa-class battleships were reactivated for gunfire support during the Korean War in the early 1950s. They were modernized in the early 1980s with Tomahawk cruise missiles, Harpoon anti-ship missiles, and Phalanx CIWS systems as part of President Ronald Reagan's 600-ship Navy program. Missouri and Wisconsin participated in Operation Desert Storm in 1991, and all four were struck from the Naval Vessel Register in 1995.