A didgeridoo is a traditional Aboriginal instrument (the natives of Australia) that exists probably since 2500-3500 years. Originally the instruments were made of eucalyptus trunks that were hollowed out by termites. Nowadays they are primarily made of bamboo or other woods.
The sound is generated - similar to brass wind instruments - through the player’s swinging lips that stimulate the air column inside the instrument. Even if the didgeridoo is a wind instrument, it is rather used for rhythmical than melodical play. Usually only the lowest swinging frequency is played and modified with particular methods like oral cavity variations, movements of the tongue or larynx.
In the Western world the didgeridoo is mostly used for meditative practices. Musicians generally use them only for unique effects. To play the didgeridoo correctly it is helpful to be proficient in circular breathing where one is exhaling through the mouth and at the same time inhaling through the nose.
The didgeridoo is perfectly for training the neck, mouth and breathing musculature and even can reduce snoring.