Short answers, pulled from the story.
Guru Tegh Bahadur was the ninth of ten Sikh gurus, leading the Sikhs from 1664 until 1675. He was born in Amritsar in 1621 as the youngest son of Guru Hargobind, and became a spiritual scholar and poet whose hymns are part of the Guru Granth Sahib.
Guru Tegh Bahadur was publicly beheaded on the 11th of November 1675 in Chandni Chowk, a market square in Delhi, on the orders of the Mughal emperor Aurangzeb.
Sources disagree on the reason. Sikh accounts say he defended the freedom of non-Muslims against Aurangzeb's intolerant policies, while Mughal accounts say he was forcibly collecting taxes from non-Muslims in Punjab. Rival family members seeking the guruship also stirred Aurangzeb's hostility toward him.
Guru Tegh Bahadur founded Anandpur Sahib in the foothills of the Himalayas in 1664, after buying the site from Rani Champa of Bilaspur for 500 rupees.
Guru Tegh Bahadur was identified through a test devised by the trader Makhan Shah Labana, who had vowed 500 gold coins to the true guru after surviving a shipwreck. Every other claimant in Bakala accepted a token offering of two gold coins, but Tegh Bahadur pointed out it fell short of the promised sum. A Sikh congregation led by Diwan Dargha Mal then installed him as guru in August 1664.
Gurdwara Sis Ganj Sahib in Chandni Chowk, Delhi, marks the site of his beheading, and Gurdwara Rakab Ganj Sahib in Delhi marks where a disciple cremated his body after burning down his own house. His severed head was carried to Punjab by Bhai Jaita and cremated at what is now Gurdwara Sisganj Sahib.