Short answers, pulled from the story.
Modern scholarship identifies Khusrau Khan, an 18th-century figure of the Mughal Empire, as the true inventor who transformed the small Persian three-stringed setar into the complex instrument known today. The instrument emerged from the Indian subcontinent in the 18th century, with the earliest written reference appearing in the 1739 work Muraqqa-i-Dehli written by Dargah Quli Khan during the reign of Muhammad Shah Rangila.
A sitar can possess 18, 19, 20, or 21 strings, creating a complex web of sound that distinguishes it from any other plucked instrument. Six or seven of these strings run over curved, raised frets and are played directly, while the remainder are sympathetic strings known as tarafdaar which run underneath the frets and resonate in sympathy with the played strings.
The sitar saw use in Western music when George Harrison played it on the Beatles songs Norwegian Wood, Love You To, and Within You Without You recorded between 1965 and 1967. Brian Jones of the Rolling Stones used a sitar on Paint It Black in 1967, and Dave Mason played it on Traffic's 1967 hits Paper Sun and Hole in My Shoe, marking a trend of featuring the instrument in pop songs described by Ravi Shankar as the great sitar explosion.
The main playing string is almost invariably tuned a perfect fourth above the tonic, while the second string is tuned to the tonic which is referred to as sa in the Indian solfège system. The perfect fifth to which one or more of the drone strings are tuned is called pañcam, not samvād, and players must re-tune for each raga adjusting the strings by tuning pegs and fine-tuning the main playing strings by sliding a bead threaded on each string just below the bridge.
The fully decorated instrumental style often called the Ravi Shankar style is typically made of seasoned toon wood and fitted with a second resonator called a tumba on the neck. The other style known as the gayaki or Vilayat Khan style prioritizes vocal imitation over visual ornamentation and was developed by Vilayat Khan into a method that imitates the melisma of the vocal style known as gayaki ang.