The frets on a guitar are numbered to make communicating easier and to allow us to use guitar tablature instead of traditional written music. The first fret is the space between the nut and the first metal strip along the fretboard. The metal strips (or fret bars) separate each fret. There are markers typically found on the 3rd, 5th, 7th, 9th, 12th, 15th, 17th, 19th, and 21st frets. These will help you navigate around the fretboard more quickly. Open strings (those that are not held down when you pluck) are referred to as fret 0.