Short answers, pulled from the story.
Modern scholarship identifies Khusrau Khan, an eighteenth-century figure of the Mughal court, as the inventor of the sitar. He developed it from the Persian setar, a small three-stringed instrument. An older attribution to the medieval poet Amir Khusrow is considered discredited by scholars.
The earliest written mention of the sitar dates to 1739, in the Muraqqa-i-Dehli, written by Dargah Quli Khan during the reign of Muhammad Shah Rangila. No text from before the eighteenth century uses the word sitar.
The word sitar is derived from the Persian sehtar, built from tar, meaning string, combined with a number. Persian instrument names used this system: dutar for two strings, setar for three, chatar for four, and panchtar for five.
A sitar can have 18, 19, 20, or 21 strings. Six or seven of these are played strings that run over the curved frets. The remainder are sympathetic strings, called tarb, taarif, or tarafdaar, which resonate beneath the frets in response to the played strings.
George Harrison played sitar on three Beatles recordings: Norwegian Wood (This Bird Has Flown), Love You To, and Within You Without You, all recorded between 1965 and 1967. Harrison began formal study of the instrument with Ravi Shankar and his protege Shambhu Das in 1966.
The two dominant modern styles are the instrumental style, sometimes called the Ravi Shankar style, and the gayaki style, associated with Vilayat Khan. The instrumental style features heavy ornamentation, thirteen sympathetic strings, and often a second gourd resonator on the neck. The gayaki style is plainer and built around a technique that imitates vocal melisma.