Short answers, pulled from the story.
Hinduism is an umbrella term for a range of Indian religious and spiritual traditions unified by adherence to dharma, a cosmic order maintained through rituals and righteous living as set out in the Vedas. It has no founder. Scholars regard it as a fusion of Brahmanical orthopraxy with various Indian cultures, with diverse roots.
The word Hindu is an exonym derived from the Sanskrit word Sindhu, the name of the Indus River and the country of its lower basin, Sindh. A Proto-Iranian sound change turned the s into an h between 850 and 600 BCE. In ancient records the term was geographical and did not refer to a religion.
Hinduism has approximately 1.17 billion followers, around 15 percent of the global population, making it the world's third-largest religion and the largest ethnic religion. Hindus live largely in India, Nepal, Mauritius and in Bali, Indonesia, with communities across South Asia, Southeast Asia, the Caribbean, the Middle East, North America, Europe, Oceania and Africa.
Scholarly studies recognise four major denominations: Vaishnavism, which worships Vishnu, Shaivism, which focuses on Shiva, Shaktism, which worships the goddess Shakti or Devi, and Smartism, which worships Shiva, Vishnu, Shakti, Ganesha, Surya and Skanda together. A 2020 estimate from The World Religion Database put Vaishnavism largest at about 399 million Hindus, followed by Shaivism at 385 million and Shaktism at 305 million.
Hinduism recognises four Purusharthas, or proper aims of human life: dharma, ethics and duties, artha, prosperity and means, kama, desires and sensory pleasure, and moksha, liberation from passions and ultimately from samsara. Dharma is considered the foremost goal and moksha the ultimate one.
Hindu texts are classified into Shruti, that which is revealed to ancient sages, and Smriti, that which is remembered and manmade. The major scriptures are the four Vedas, the Upanishads, the Puranas, the Mahabharata including the Bhagavad Gita, the Ramayana and the Agamas. The Puranas began to be composed from about 300 CE onward.
The Kumbh Mela is a major Hindu pilgrimage on the eve of the solar festival Makar Sankranti, rotating every three years among four sites: Prayagraj, Haridwar, Ujjain and Nashik. It is one of the world's largest mass pilgrimages, with an estimated 40 to 100 million people attending to pray to the sun and bathe in the river, a tradition attributed to Adi Shankara.