The number and placement of frets on an instrument's neck determines its scale length and tuning. The most common fretting system is called "equal temperament", which divides the octave into 12 equal half-steps. This system is used on most Western musical instruments, including guitars, violins, and cellos.
Other fretting systems include "just intonation", which tunes the intervals between notes according to their natural harmonic relationships, and "pythagorean tuning", which is based on the ratios of small whole numbers.
Frets can be made of a variety of materials, including metal, plastic, and bone. The most common type of metal fret is nickel silver, which is an alloy of nickel, copper, and zinc. Plastic frets are often used on electric guitars because they are less expensive and easier to install than metal frets. Bone frets are considered to be the highest-quality fret material, and they are often used on acoustic guitars.
The size and shape of frets can also vary. Some frets are tall and narrow, while others are short and wide. The height and width of frets can affect the feel and playability of an instrument.
Frets are an essential part of many stringed musical instruments, and they play an important role in determining the instrument's sound and tuning.