A maypole is a tall, sometimes highly decorated, wooden pole used in various European folk festivals - around which a 'maypole dance' often takes place.
Historically, maypoles are believed to have originated in Germanic Europe, but are now commonly found in Malta, Germany, Austria, Nordic countries, Belgium, Britain, United States, Italy and Canada (amongst others).
The origins of the Maypole tradition are unknown.
Various theories have been put forward, including that they were "a remnant of the Germanic reverence for sacred trees", or that they were perhaps pagan phallic symbols. Other scholars say there is no evidence for either theory.
See: Wikipedia