Short answers, pulled from the story.
Soviet is derived from a Proto-Slavic root meaning "to inform" and carries meanings in Russian including council, assembly, advice, and harmony. The related word "sovietnik" means councillor, formed by attaching the occupational suffix -nik to "soviet."
According to the official Soviet historiography, the first workers' council formed in Ivanovo, northeast of Moscow, in May 1905 during the 1905 Russian Revolution. The anarchist Volin claimed in his memoirs that he had witnessed the beginning of the St Petersburg Soviet as early as January 1905.
In 1917, soviets formed across Russia and established a situation of dual power alongside the Provisional Government. The Bolsheviks grew in influence as the Provisional Government failed to end the war, and the Second Congress of Soviets declared itself the supreme governing body of Russia in October 1917. A formal electoral code adopted in March 1918 set the terms for who could participate in the soviets going forward.
Delegates to local soviets were elected by a show of hands at open factory and village meetings, where every candidate was personally known to the voters. Any delegate who failed to represent the electorate's views could be recalled by majority vote; in Moscow alone, fifteen delegates were recalled within four years during the 1930s. By 1985, nearly 2 million deputies served on standing committees, representing roughly 80 percent of all deputies.
The Bavarian Soviet Republic was a short-lived workers' council government established after Kurt Eisner, who had led a bloodless coup on the 7th of November 1918, was assassinated three months later. The German Army and Bavarian Freikorps overthrew the republic on the 1st of May 1919, killing several hundred people. The upheaval became the political springboard for Adolf Hitler, who described his opposition to the soviet state in Mein Kampf.
Soviets formed in several countries beyond Russia. In Poland, over 100 workers' councils assembled around 500,000 participants between 1918 and 1919 but were dismantled by July 1919. The Limerick Soviet appeared in Ireland in 1919. In China, the Chinese Soviet Republic was declared in 1931 and dissolved on the 22nd of September 1937 under the terms of the Second United Front.