an acoustic guitar is a string instrument. it has six strings which pass from tuning pegs over the instrument's neck which is marked with lines called frets. these marks show where to press a string with the fingers of the left hand, to change the note that string plays. the right hand plucks or strums the strings, either with the fingers or using a plectrum ("pick"), to make them sound. acoustic guitars are used in types of music ranging from classical to rock and roll, to bluegrass and folk. the six strings can be steel or nylon. nylon strings are typically used for classical and related styles of music. steel strings are typically used for most other styles.