Full moon day during Ashadha month is known as Guru Purnima day. Traditionally this day is reserved for Guru Puja or Guru Worship. On this day disciples offer Puja or pay respect to their Gurus. Guru refers to spiritual guide who enlighten disciples by his knowledge and teachings.
Guru Purnima is also known as Vyasa Purnima and this day is commemorated as birth anniversary of Veda Vyasa. Veda Vyasa was the author as well as a character in the Hindu epic Mahabharata.
Adi Shankara, Sri Ramanuja Acharya and Sri Madhvacharya are some of the noteworthy Gurus in Hinduism.
Guru Purnima is also celebrated by Buddhists in the honor of Gautama Buddha to commemorate the day when Buddha gave his first sermon at Sarnath, Uttar Pradesh, India.