The neck of the guitar can be made at many different lengths and shapes. The neck has tuning machine heads at the top of it for tuning the strings and a tension bar inside of it to adjust the tension on the guitar once strings are put onto it. The neck can also be decorated with various types and shapes of inlays, such as pearl and mother of pearl. Also, some necks go all of the way through the guitar and others stop a couple inches in. The length depends on how the guitar was made.

Picture courtesy of www.GuitarShop.net