Pushtimarg (The Path Of Grace) is a sect of the Hindu religion, founded by Shrimad Vallabhacharya (known as Mahaprabhuji) around 1500 AD.
Shri Vallabhacharya is one of the five main Acharyas of the Hindu Religion. (The other four being Shankaracharya, Shri Ramanujacharya, Shri Madhavacharya and Shri Nimbarkacharya.) He propagated the philosophy of Shuddhadvaita which forms the basis of Pushtimarg devotional practice.
These acharyas have made significant contribution to the bhakti movement and led to the medieval rise in popularity of the Hindu Religion. The devotional movement is based on the idea that love of God should be seen as an end in itself, not as a means to something else.
Shri Vallabhacharya was born into a very noble and learned Brahmin family in South India in what is today called Andhra Pradesh. His ancestors had a very staunch religious background and included learned Brahmins like Shri Yagnanarayan Bhatt and Shri Ganapati Bhatt. They wrote several books on religion and devotion. Shri Vallabhacharya was the second son of Lakshman Bhatt and Yallammagaru. Their ancestors had performed several Soma-yagnas and Shri Lakshman Bhatt completed 100 Somyagnas. Shri Yagnanarayan was blessed by Lord Vishnu, that on completion of 100 Soma-yagnas, God himself would incarnate in his family.
Thus when 100 Soma-yagnas were complete, Lakshman Bhatt went to Kashi to accomplish his vow of feeding 125,000 Brahmins. He could not complete this task as there were political disturbances in Kashi. He took his pregnant wife Yallammagaru and on his way southwards he halted at a place called Champaranya. There, his wife gave birth to a still baby which they kept under a tree and proceeded ahead. On the same night Lakshman Bhatt heard a celestial voice ordering him to go back to the baby and pick it up as it was misunderstood to be a still born. That baby was no ordinary one, but by the grace of God, Shri Vallabh had taken birth through Yallammagaru's womb. On reaching the spot where they had kept the baby, they found the baby encircled by a divine fire as a protecting spirit.
Shri Vallabh was a brilliant and extraordinary child. He finished studying all the Vedas and all the prominent scriptures at a very early age. At the age of 11 he started his all India pilgrimage. During this tour he came to Vijaynagar where he came to know about a sensational debate that was being conducted in the court of King Krishnadevraya. The debate was between the different Acharyas over the question whether the relationship between the world and God is dualistic or non-dualistic. Shri Vallabh entered the court and with his unopposed arguments proved that God is pure and non-dualistic i.e. Shuddhadwait. His philosophy thenceforth came to be known as Shuddhadwait Brahmvaad. The details of which can be found in a book named "Vallabh Digvijay"
During the second pilgrimage, Lord Krishna appeared in the form of Lord Shrinathji in front of him and ordered him to reestablish Pushti Marg and propagate the pushti kind of devotion among the chosen ones and bring them back to their original state in God's own domain. i.e. Vaikuntha or Golok-dham . But the question in Shri Vallabh's mind was that the divine souls in this world too are highly influenced by the materialistic world and their souls and body have lost the kind of purity that is needed for their reunion with the Supreme entity i.e.. Lord Krishna.
Lord Shrinathji assured him that with "brahamasambandha", (relationship with God) whichever soul is admitted into the Pushti marg, all its impurities will refrain from obstructing the soul's relation with Himself and the soul will be eligible to pursue His bhakti. That was the night of Pavitra Ekadashi (Four days before the new moon day) of the auspicious month of Shravana. Lord Shrinathji taught him the Brahamasambandha mantra and asked him to bring back the divine souls back to him.
On the following day Shri Vallabhacharya initiated his first disciple Shri Damodardas Harsani with this mantra along with the principles of Pushtimarga. This was how Pushtimarga was established.