Short answers, pulled from the story.
419 million people have no access to a toilet at all and must openly defecate and urinate. One billion people in developing countries have no toilets in their homes, which is why providing sanitation services to everyone by 2030 is a target of Sustainable Development Goal 6.
Flush toilets use water to remove waste, while dry or non-flush toilets do not. Flush toilets connect to a sewer system or septic tank, whereas dry toilets connect to a pit, removable container, composting chamber, or other storage and treatment device.
The water in a toilet bowl connects to a pipe shaped like an upside-down U, where the standing water acts as a barrier to sewer gas entering the building. Sewer gas instead escapes through a vent pipe attached to the sewer line. The S-trap, invented by Scottish mechanic Alexander Cummings in 1775, uses the same standing-water seal.
The earliest known internal pit toilet is at the city of Uruk in Mesopotamia, from around 3200 BC. The Indus Valley Civilisation built the world's first known urban sanitation systems, with toilets set into the outer walls of homes at Mohenjo-Daro around 2800 BC.
Toilet was a French loanword first attested in 1540, originally meaning the toilette or little cloth draped over the shoulders during hairdressing. It later described grooming at a dressing table, then by 1819 a grooming room, and finally became a euphemism for rooms and fixtures used for urination and defecation.
A pig toilet consists of a toilet linked to a pigsty by a chute and is still in use to a limited extent. It was common in rural China, where the Han dynasty used pig toilets two thousand years ago, and was known in Japan, Korea, and India.
A precursor to the flush toilet was designed by John Harington in 1596, though such systems were not widely used until the late nineteenth century. The water closet took its known form around 1770 through the work of Alexander Cumming and Joseph Bramah, and William Elvis Sloan invented the Flushometer in 1906.