Depending on the construction of the instrument they are used on, strings will usually have either a ball or loop at one end to attach the string to the instrument. Strings for some instruments may be wrapped with silk at their ends to protect the string. The color and pattern of the silk can be used to identify the string.
The tone of a string depends on its weight, and, therefore, on its diameter or so-called gauge. Traditionally, diameter is measured in thousandths of an inch. The larger the diameter, the heavier the string is. Heavier strings require more tension for the same pitch and are consequently harder to press down to the fretboard. Heavier strings will also produce a louder and thicker tone. (If a fretted instrument is restrung with different string gauges, it may be necessary to adjust the height of the string above the frets, called the "action", in order to make the instrument easier to play or to avoid the strings buzzing against the frets.)
The following are common strings for violins. Click on the pictures for more information about each string.