Baby boomers and Luddites excused, who among us has not heard of PayPal - especially with the near saturation of e-commerce in many markets?
Before delving into the technicalities of PayPal, it's best if we understand a bit about the company's history.
PayPal's history begins with the inception of the internet financial services company X.com founded by Elon Musk among others around 2000. By March of that year, X.com acquired Confinity (founded by Peter Thiel and Max Levchin) and the rights to its PayPal system (the gateway was launched only in October 1999). The company renamed itself as PayPal on June 2001 to focus exclusively on internet transactions - particularly on the popular e-shopping portal eBay.
In February 2002, PayPal became the first tech company to go for an IPO after the 9/11 attacks. On 3 October 2002, eBay acquired PayPal for a brisk $1.5 billion - thereby consolidating eBay's hold of online payments and seamlessly integrated the preferred payment means into its shopping portal (as early as April 2000, over 1 million eBay users were already using PayPal for transactions).
Today, the gateway boasts an astounding 100 million active accounts with coverage in over 190 countries around the world. However, the availability of accounts, payment options, fees and other particulars varies from country to country. For that, do refer to their official policies: https://www.paypal.com/us/webapps/mpp/country-worldwide

For starters, PayPal is the internet's largest and most popular payment gateway. Payment gateways, or e-commerce payments systems, are essentially online portals that facilitate electronic transfers of money for online transactions. Gateways serve as alternatives to traditional payment methods like cheques, credit/debit cards and have even swallowed some of the pie away from internet and mobile banking.For companies like PayPal, they act as intermediaries between those who buy (whether individual consumers or businesses) and those who sell (individual or business). PayPal and other gateways (don't forget banks) use sophisticated encryption software involving "tokens" to facilitate money transfer.