Full moon day in Ashadha month is observed as Guru Purnima day. Traditionally this day is earmarked for performing Guru Puja or Guru Worship. On this day disciples offer Puja and pay respect to their Gurus. Guru here refers to spiritual guide who enlighten his disciples by his knowledge and teachings.
Guru Purnima is observed as Vyasa Purnima, the birth anniversary of Veda Vyasa, who was the famous creator of the popular Hindu epic Mahabharata.
There are several significant Gurus in Hinduism. Adi Shankara, Sri Ramanuja Acharya and Sri Madhvacharya are few among them.
After enlightenment, Buddha gave his first sermon at Sarnath in Uttar Pradesh. Buddhists celebrate this day as Guru Purnima.