The term Guru is split as ‘Gu’ and ‘Ru’. Gu denotes ignorance and Ru means that which helps one to over come ignorance. According to the established traditions, the parents are instrumental in giving birth to a child in this material world but it is the Guru who enlightens one and helps one to overcome the material bondage and become liberated from this trans-migratory existence of birth, death, old age and disease.
Guru Poornima is also called as Vyasa-Poornima because all the schools of theistic philosophy that have originated in the country have their source in the scriptures classified or compiled by Veda Vyasa. Veda Vyasa classified the Vedas into four, based on their content and the purpose for which they are recited, compiled eighteen Puranas, authored Brahma Sutras and Mahabaratha, which is considered to be the essence of all Vedas, for the benefit of people who are not knowledgeable in the Vedas.
Like parents only a true guru can selflessly think of the welfare of his disciples at the cost of his own interests. In the fifth canto of Srimad Bhagavatam Vrishaba Deva says that one should not become a guru unless he has the ability to liberate his disciple. Therefore an ideal guru should also be well versed in the knowledge that leads to Brahman. A selfish person cannot realize Brahman. Therefore, unless one has overcome his selfishness and is interested in the welfare of his disciples one cannot become a true guru even if he is well versed in all the scriptures.