What was the Taiping Rebellion?

I came across this Chinese Civil War that lasted from 1850 to 1864 that killed 20 million people. A Christian Chinese guy named Hong Xiuquan got a few things mixed up, decided he was Jesus, and then got some followers together. He then decided to make a new Chinese Empire to destroy the Qing. What was going on in China from 1850 to 1864 that led to the deadliest war in human history?