Short answers, pulled from the story.
Bilibili was founded on the 26th of June 2009, by Xu Yi, known online as "9bishi". He originally launched it as a fan site called Mikufans.cn before relaunching it as Bilibili on the 14th of January 2010.
Bilibili is a nickname for the character Mikoto Misaka, the protagonist of the anime A Certain Scientific Railgun. The name was chosen when Xu Yi relaunched his fan site as a general video-sharing platform in January 2010.
Danmu, meaning "bullet curtain", is Bilibili's real-time commenting system where user messages scroll across the video screen as overlaid text. Comments typically move from right to left, and users can post in three formats: rolling, top-aligned, or bottom-aligned.
Bilibili listed on the NASDAQ on the 28th of March 2018, following a planned IPO of up to US$400 million. It made a secondary listing on the Hong Kong Stock Exchange on the 29th of March 2021, at an opening price of HK$790 per share, raising US$2.6 billion.
In the third quarter of 2022, Bilibili's average monthly active users reached approximately 332.6 million, including 28.5 million paying subscribers.
Bilibili's mascots are named 22 and 33, elected by community vote between the 7th of July 2010, and the 16th of August 2010. Both received exactly 1,824 votes each from 72 submitted artworks, so Bilibili declared both winners and named them after their election serial numbers.