Shakuhachi are made from the root end of madake, a strong, non-splitting species of bamboo.
The word shakuhachi means a length of 1 shaku and 8 sun. 1 shaku is just over 30 cm. This is the standard length. However shakuhachis can be of any length, limited only by the size of the hand. Most are between 1.6 shaku and 3 shaku.
There are 5 finger holes, 1 at the back and 4 at the front.
The key to its special sound is the bore shape, dictated largely by the bore of the root end of madake.

History of Shakuhachi
Came to Japan from China during the 6th century
During Tokugawa period, used by komuso (priests of nothingness) as a spiritual tool (Honkyoku)
After Meiji restoration, secular schools became popular, and sankyoku or gaikyoku (ensemble pieces) gained popularity.
Originally played only by Japanese male priests of the Fuke sect of Zen Buddhism, it is now played by men and women around the world in many contexts, both spiritual and secular.

Different techniques
Sound is produced by blowing across the mouthpiece (similar to blowing across the top of a bottle)
Using just the 5 holes, a pentatonic scale is produced (D,F,G,A,C on the standard length instrument).
Extra pitches are produced by cross fingering, shading of holes and most importantly, by lowering and lifting the head (kubi furi) or meri-kari (メリカリ).
Tone colour changes are important, and are achieved with meri-kari, and blowing techniques.