Short answers, pulled from the story.
Hong Xiuquan, a Hakka farmer who failed his imperial examinations three times in 1837, founded the movement. He claimed to have had visions of Heaven that led him to adopt the name Hong Xiuquan and believe he was the younger brother of Jesus Christ.
The rebellion began in early January 1851 when rebel forces routed Qing troops at Jintian and ended with the defeat of the last army by Li Fuzhong on the 29th of January 1866. The main conflict lasted almost 14 years until August 1871 when government forces wiped out the final resistance in the border region of Hunan, Guizhou and Guangxi.
Hong Xiuquan died in June 1864 after contracting food poisoning from eating wild vegetables while the city was under siege. His body was exhumed on the 1st of August 1864, dismembered, cremated, and its ashes were fired from a cannon as spiritual punishment ordered by Zeng Guofan.
Estimates suggest total deaths reached approximately 20 to 30 million civilians and soldiers over the course of the rebellion. Most deaths were attributed to plague and famine rather than direct combat, though some analysts claim the toll may have reached 100 million.
Western intervention occurred because the Taiping government refused cooperation regarding Shanghai and occupied Ningbo in December 1859. British and French forces intervened due to fear that a successful rebellion would create a stronger China able to resist Western power.