It originated in Spain in the late 18th century and is danced by either a soloist or a couple. It is in a moderately slow tempo, and is performed to music which is sung and accompanied by castanets and guitars. It is in triple time, and usually has a triplet on the second beat of each bar. A number of classical composers have written works based on this dance: Frederic Chopin wrote a bolero for solo piano, and Maurice Ravel's Bolero is one of his most famous works, originally written as a ballet score but now usually played as a concert piece.
In Cuba, the bolero developed into a distinct dance in duple time which eventually spread to other countries. In the 1950s, sung boleros became extremely popular and have enjoyed enduring popularity as a popular song form throughout Latin America.
A bolero can also be an item of clothing -- a short jacket with long sleeves, normally worn by men.