The Guitar is a 6 stringed musical instrument (although variates can come with 7 or even more strings en bridge) which is plucked by a plectrum (pick) or finger picked to produce sound. Changing the string open length via fretting allowed its player to change the tones frequency accordingly.
Guitars and its variations were moderately used in the last several centuries mainly for the preference and composition of complex and technical classical music while using its radiatively large tonal range and plucking sound compared to other popular instruments. Guitars took its current popularity after seeping into blues, jazz and everyday music in the 20th century United States and by creating the electric guitar (and subsequently the electric bass). This popularity grew until almost everyday band/genre in contemporary music employ this instrument.