Short answers, pulled from the story.
The Indian subcontinent is a physiographic region of Asia that projects into the Indian Ocean between the Bay of Bengal and the Arabian Sea. In its core definition it comprises Bangladesh, India, and Pakistan. In an extended usage, Bhutan, the Maldives, Nepal, and Sri Lanka are also included.
Citizens of Pakistan, which became independent in 1947, and Bangladesh, which became independent in 1971, often perceive the term as offensive because it places India's name over the entire region. As a result, the phrase is used less and less within those two countries.
Written evidence for the term dates from the early twentieth century, when most of the territory was either part of the British Empire or allied with it. It served as a convenient label for both British India and the princely states collectively.
Indian subcontinent is a geophysical term referring to the landmass below the Himalayas, while South Asia is a geopolitical designation. South Asia is the more common usage in Europe, North America, and often within the region itself, and it frequently includes Afghanistan, which is not considered part of the subcontinent.
The Himalayas formed when the Indian plate, after rifting from Gondwana, drifted northward and collided with Eurasia, closing the Neo-Tethys Ocean. The suture zone marking that collision is called the Indus-Yarlung suture zone, and it lies north of the Himalayas.
The Indus-Yarlung suture zone is the remnant of the Neo-Tethys subduction zone, pinched between the Indian and Eurasian continental crusts where the two plates welded together. It lies north of the Himalayas, and both the Indus River and the Yarlung Tsangpo flow along it.