X.com

X.com was an online bank co-founded by Elon Musk, Harris Fricker, Christopher Payne, and Ed Ho in March 1999. In March 2000, X.com merged with Confinity Inc., a software company based in Silicon Valley. Musk was attracted to Confinity because of its easy payment system. The merged company changed its name to PayPal. eBay bought PayPal for US$1.5 billion in 2002. In July 2015, PayPal was spun off and became an independent company.
Business model.
X.com was one of the world's first online banks, and deposits were insured by the FDIC. The company was initially funded by Elon Musk and Greg Kouri, who went on to fund Musk's later ventures: Tesla and his startup, SpaceX.
History.
During X.com's early years, a power struggle ensued between Musk and Fricker, which resulted in Fricker attempting a coup on X.com to become the company's CEO.
In March 2000, X.com merged with Confinity, its fiercest competitor, the new company being called X.com. Musk was its biggest shareholder and was appointed as its CEO. Started in 1998, Confinity's product PayPal enabled users having Palm Pilots to send money to each other through its infrared ports. Subsequently, PayPal developed to allow users to send money using email and the web.
In October 2000 Musk was replaced by Peter Thiel, the co-founder of Confinity. In June 2001, X.com was renamed PayPal.
On October 3, 2002, eBay purchased Paypal for $1.5 billion.
In July 2015, PayPal was spun off to become an independent, publicly-traded company. 
On 5 July 2017, Musk repurchased the domain name X.com from PayPal. He explained later that he bought the website because "it has great sentimental value".
On 14 July 2017, X.com was launched again, consisting of a blank white page with one "x" in the top left corner, and a custom error page displaying a "y". The site displays this way due to having nothing in its source code except the single letter "x". In December, X.com redirected visitors to The Boring Company's website, which Musk also owns. This was done in order to advertise a hat sale.
X.com no longer redirects to The Boring Company, having reverted to the previous state of the blank page with one "x" in the top left corner. Subpages redirect to a blank page with a "y" in the same corner.