Short answers, pulled from the story.
The Indus Valley Civilisation was a Bronze Age civilisation in the northwestern regions of South Asia, lasting from 3300 BCE to 1300 BCE and in its mature form from 2600 BCE to 1900 BCE. Together with ancient Egypt and Mesopotamia, it was one of the three early civilisations of the Near East and South Asia, and the most widespread of the three. It is also called the Harappan civilisation, after its type site Harappa.
The Indus Valley Civilisation flourished in the alluvial plain of the Indus River and along the Ghaggar-Hakra river system, spanning much of Pakistan, northwestern India, and northeast Afghanistan. At its height it extended from Balochistan in the west to western Uttar Pradesh in the east, and from northeastern Afghanistan in the north to Gujarat in the south. Its five major urban centres were Mohenjo-daro, Harappa, Ganeriwala, Dholavira, and Rakhigarhi.
Charles Masson, a deserter from the East India Company's army, left the first modern accounts of the ruins, discovering Harappa in 1829 and publishing his observations in 1842. The civilisation was formally recognised by John Marshall, who announced the discovery in the Illustrated London News on the 24th of September 1924. Systematic excavation of Mohenjo-daro began in 1924-25 under K. N. Dikshit.
Many scholars attribute the decline to an abrupt mega-drought and cooling about 4,200 years ago, which marks the onset of the Meghalayan Age. The rain-fed Ghaggar-Hakra system depended on monsoons that weakened from about 1800 BCE, making flood-based agriculture unsustainable. Signs of decline appeared around 1900 BCE, and by about 1700 BCE most cities had been abandoned as people migrated east toward the Ganges basin.
Indus cities were laid out on a highly uniform grid and featured the world's first known city sanitation systems, with covered drains lining the major streets and wells supplying water to homes. Their architecture included dockyards, granaries, warehouses, brick platforms, and massive protective walls, but no large monumental palaces or temples. The two largest centres, Mohenjo-daro and Harappa, very likely grew to hold between 30,000 and 60,000 people each.
The Indus script remains undeciphered, and it has not even been demonstrated to be a true writing system. Between 400 and as many as 600 distinct symbols have been found on stamp seals, tablets, and pottery, with most inscriptions about five characters long and the longest, on a copper plate, carrying 34 symbols. A 2009 study by P. N. Rao and colleagues found the symbol patterns closer to spoken words, but other scholars dispute that it encodes language.