Short answers, pulled from the story.
Bolshevik comes from the Russian word boljšinstvó, meaning majority. The name arose after Lenin's faction won the majority of key votes at the 2nd Congress of the RSDLP in 1903. The rival Menshevik name comes from menjšinstvó, meaning minority.
The split began at the 2nd Congress of the RSDLP, held in Brussels and London in August 1903, over a dispute between Lenin and Julius Martov about party membership rules. The factions permanently broke relations in January 1912 after the Bolsheviks held a Bolsheviks-only Prague Party Conference and expelled the Mensheviks.
The Bolsheviks used bank robberies, donations from wealthy supporters, and membership funds. A 1907 robbery netted the party over 250,000 roubles, roughly equivalent to $125,000. Lenin also paid professional revolutionaries salaries from party funds so they could dedicate themselves full-time to the cause.
What Is to Be Done? was a political pamphlet Lenin wrote in 1901 and published in Germany in 1902. It argued that revolution required a disciplined corps of professional revolutionaries rather than a broad membership, a position that directly caused the split with the Mensheviks at the 1903 Congress.
Bolshevik figures Anatoly Lunacharsky, Moisei Uritsky, and Dmitry Manuilsky stated that while Lenin's influence on the party was decisive, the October insurrection was carried out according to Trotsky's plan, not Lenin's.
The Bolsheviks became the Communist Party of the Soviet Union through a series of renamings. They became the Russian Communist Party (Bolsheviks) in 1918, the All-Union Communist Party (Bolsheviks) in 1925, and finally the Communist Party of the Soviet Union at the 19th Party Congress in 1952.