Bugles are a military instrument, often found in military marching bands. They consist of one tube of metal, e.g. brass, coiled twice and widened at the "business end" just as a trumpet is. Bugles are often plated with a silver-coloured finish (probably an alloy, exactly what I'm not sure). At the opposite end to the horn there is a detachable mouthpiece, which can vary in style and are interchangeable to suit individual Buglers' tastes, attached by a chain. The mouthpiece can be moved in and out of the main body and held in place by a screw on the exterior, which tunes the instrument. Tassels are often attached to help carry the bugle and for decorative purposes (eg RM bands have red, blue and gold tassels). Bugles produce an unmistakable sound, even to the untrained ear, and have been in use for centuries.
The best example of buglers in a modern marching band are the Buglers of the Royal Marines Bands of the UK. Training for these men takes one year and eight months, for around 6 hours a day, and they fulfil the role of Drummers at the front of the bands as well as bugling and playing the E-flat herald trumpet when required. This may not sound like much, but try playing a bugle for even half an hour without breaks and you'll know how hard it is. I played the bugle for seven years in a marching band, but even at my peak only practiced twice a week and my lips got tired quickly.
Anybody who has ever seen a Royal Marine band in concert knows that the Buglers perform their ceremonial duties with typical precision and excellence. After all, many people go to these concerts just for the spectacle, let alone the music (which, of course, is brilliant). The bugle marches of RM bands include "Silver Bugles", "Zeebrugge" (a Royal Marine Memorable Date and Battle Honour) and "Per Mare Per Terram" (the RM motto; "By Sea By Land"), and others include "Mechanised Infantry". Buglers also perform Naval Sunset ceremonies, the tune played being "Sunset", suprisingly, and also play the "Last Post" at occasions, such as the returning of Hong Kong to China in 1997 (I have personally met the RM Bugler who played at this ceremony; he came to my school one day to help train us bunglers in the school band). Most notable of events involving the "Last Post" being sounded are Remembrance Sunday and Armistice Day (November 11th, the end of the First World War), both commemorating the dead of the wars of the twentieth century. The notes of the British version of the "Last Post" serve as a moving and poignant reminder of the conflicts in which men died for us; for those listening and, especially, for the bugler. Believe me, I know how it feels (playing at the funerals of ex-servicemen has much the same effect).
Bugles are still used as regimental instruments by The Royal Green Jackets due to the regiment's history, and continue to exist in other marching bands despite the relative difficulty of playing compared to valve instruments such as the cornet. Bugles cost something in the region of £200-250, fairly cheap in comparison to trombones etc, reflecting the small size and simplicity of design. The bugle remains a firm part of military tradition, providng vital services as well as being one of the most difficult instruments to learn, although only five notes are regularly used (and the lowest G is only used in the "Last Post" and rarely anywhere else).