A music festival is a festival oriented towards music that is sometimes presented with a theme such as musical genre, nationality or locality of musicians, or holiday. They are commonly held outdoors, and are often inclusive of other attractions such as food and merchandise vending machines, performance art, and social activities. The Pythian Games at Delphi included musical performances, and may be one of the earliest festivals known. During the Middle Ages festivals were often held as competitions. Many festivals are annual, or repeat at some other interval. Some, including many rock festivals, are held only once. Some festivals are organized as for-profit concerts and others are benefits for a specific cause. Another type of music festival is the educative type, organised annually in local communities, regionally or nationally, for the benefit of amateur musicians of all ages and grades of achievement. While entrants perform prepared pieces in the presence of an audience which includes competitors, the essential feature of this type of festival is that each participant receives verbal and written feedback, there and then, from a highly qualified, professional adjudicator — someone whom they might never meet in any other way. They also usually receive a certificate, classified according to merit, and some may win trophies. The competitive element is often played down, however, as the important aspect is that participants can learn from one another. Such festivals aim to provide a friendly and supportive platform for musicians to share in the excitement of making music. For many they provide a bridge between lessons & examinations and performing confidently in public.