Guru Purnima is celebrated in honour of all Gurus, since Guru or Teacher is held in high esteem according to Sanatana Dharma. Veda Vyasa who authored Mahabharatha and also classified the Vedas is known as Adi Guru. Veda Vyasa was born to Rishi Parashar and Matsyagandha on this very day, so this is also known as Vyasa Purnima.
On Vyasa Purnima, the shishya (student or devotee) offers obeisance to his or her Gurus. In Sanskrit, ‘Gu’ means darkness and ‘Ru’ means to remove darkness or ignorance. A Guru therefore is one who dispels darkness from one's life by providing the light of knowledge. A Guru leads us on our journey of discovering the Supreme.
We chant the shloka:
Gurur Brahma Gurur Vishnu Gururdevo Maheshwaraha
Guruhu sakshat Parambrahma tasmai Shri Gurave namaha.
It means that the Guru encompasses Brahma, Vishnu and Shiva and I bow to that supreme teacher or Parabrahma.
This shloka shows the importance assigned to a Guru in Sanatana Dharma.
Sanatana Ireland is celebrating this year's Gurupurnima on Tuesday, 19th July.