Short answers, pulled from the story.
The swing era ran from 1935 to 1946. Benny Goodman's Palomar Ballroom performance on the 21st of August 1935 is widely regarded as the moment swing became America's dominant popular music, and the era wound down after the war through a combination of wartime restrictions, recording bans, and shifting tastes.
The major swing era bandleaders include Benny Goodman, Duke Ellington, Count Basie, Jimmie Lunceford, Cab Calloway, Benny Carter, Jimmy Dorsey, Tommy Dorsey, Earl Hines, Bunny Berigan, Harry James, Lionel Hampton, Glenn Miller, and Artie Shaw. Fletcher Henderson was also central to the era's development, supplying arrangements to Goodman after his own orchestra folded in 1934.
Fletcher Henderson's orchestra, beginning in 1923, pioneered the call-response brass-and-reed arrangements and soloist-focused style that defined swing. When Louis Armstrong joined in 1924, the emphasis on individual soloists intensified further. After the Great Depression forced Henderson's band to fold in 1934, he sold his arrangements to Benny Goodman, directly fueling Goodman's success.
Swing dancing originated in the late 1920s as the Lindy Hop and became inseparable from hot swing music throughout the swing era. Competitive jitterbuggers gathered at swing ballrooms and the dance was popular enough to appear in newsreels and films. The professional troupe Whitey's Lindy Hoppers appeared in Hellzapoppin' in 1941 and other films. Swing dancing outlived the swing era and later became associated with R&B and early rock and roll.
Several forces converged simultaneously. A 1941 ASCAP royalty dispute banned a large portion of swing repertoire from radio for over a year. A recording ban by the American Federation of Musicians halted instrumental recording from July 1942 until November 1944. Wartime travel restrictions and military conscription strained touring big bands. A 30% federal excise tax on dancing nightclubs imposed in 1944 undercut the market for dance music in smaller venues.
Gypsy swing was developed in Europe by guitarist Django Reinhardt and violinist Stephane Grappelli, drawing on French popular music, gypsy songs, and Reinhardt's own compositions including "Minor Swing". Unlike American big band swing, gypsy swing uses no brass or percussion; guitars and bass form the backbone, with violin, accordion, clarinet, or guitar taking the lead. Groups typically number no more than five players.