Short answers, pulled from the story.
BitTorrent was designed by programmer Bram Cohen, a University at Buffalo alumnus, in April 2001. He released the first version on the 2nd of July 2001. Cohen and Ashwin Navin later founded BitTorrent, Inc. in 2004 to continue developing the technology.
BitTorrent accounted for a third of all internet traffic in 2004, according to a study by Cachelogic. By early 2015, AT&T estimated that BitTorrent still accounted for 20% of all broadband traffic. As of 2019, Sandvine reported it generated 27.58% of upstream traffic.
BitTorrent v1 uses the SHA-1 hashing algorithm, which is no longer considered safe from collision attacks. BitTorrent v2, released in 2017, uses SHA-256 and a Merkle tree structure for more precise integrity checks. A hybrid format supports both v1 and v2 clients from a single torrent file.
The BitTorrent protocol itself is legal. Legal problems arise from using it to distribute copyrighted material without authorization. In the United States, more than 200,000 copyright infringement lawsuits have been filed related to BitTorrent since 2010.
Facebook and Twitter use BitTorrent to distribute updates to their own servers. Blizzard Entertainment previously used it for patches to World of Warcraft, StarCraft II, and Diablo III. The Internet Archive added BitTorrent download options for more than 1.3 million files in August 2012. The British government also used it to distribute information about public spending.
In August 2007, Comcast was found to be actively preventing BitTorrent seeding by monitoring and interfering with peer communications. In 2008, Comcast reached a settlement with BitTorrent, Inc. agreeing to manage traffic in a protocol-agnostic way. The episode intensified the debate over net neutrality in the United States.