SRILA PRABHUPADA: Krishna went to His father's house, and He came to Kuruksetra in the chariot. This is Ratha-yatra. And Radharani and the inhabitants of Vrindavana, their only business was... After Krishna departed from Vrindavana to Mathura and He never returned... Once He returned. So mother Yashoda, the cowherd boys and the gopis, they lost their life and vital force. So they were simply crying and weeping. That was their business.
So Krishna sent sometimes Uddhava to pacify them, that "I am coming very soon after finishing My business." So when they got this opportunity that "Krishna has come to Kuruksetra with His brother, sister, father. So let us go and see..." So they went to Kuruksetra to see Krishna. Whenever they got some opportunity, they wanted to see. Just like these cowherds boys, when there was Battle of Kuruksetra near Delhi... Vrindavana is not far away from Delhi. It is about ninety miles.
So they went to see Krishna in the charioteer fighting dress. They were astonished. They thought that "Krishna is our friend, cowherd boy. How is that, He is in the chariot fighting?" So they became astonished. So this is the pastimes of Vrindavana. So similarly, when the inhabitants of Vindavana went to see Lord Krishna, Jagannatha... Krishna means Jagannatha. Jagat. Jagat means this world, and natha means master, or proprietor. So Krishna says in the Bhagavad-gita, bhoktaram yajna-tapasam sarva-loka-mahesvaram: [Bg. 5.29] "I am the proprietor of all the planets." Therefore He is Jagannatha. Jagannatha means the proprietor of all the world, all the planets.
So the Vrindavana inhabitants went to see Krishna because their life was Krishna. They did not know anything except Krishna. So that was the opportunity. So it was the request of Radharani to Krishna, "My dear Krishna, You are the same Krishna; I am the same Radharani. We are meeting, but We are not meeting in the same place. Here You are, just like a royal king with chariots, with soldiers, with Your ministers, secretaries. And there in Vrindavana You were a cowherd boy, and We used to meet in the jungles, in the bushes. So I want to take You there. Then I will be happy."
So that sentiment was expressed by Lord Caitanya, because Lord Caitanya's worship was in the mood of Radharani."
Ratha Yatra is more than 5000 years old
After spending the first 16 years of His manifest pastimes on his earth in intimate loving exchanges with the residents of Vrindavana, especially the gopis, Krishna never returned to Vrindavana from Mathura and Dwaraka. So, when the gopis came to know that Krishna along with Balarama and Subadhra were coming to Kurukshetra from Dwaraka on the occasion of the solar eclipse, They became anxious to meet him. When they met Krsna, surrounded by all his queens and associates in great opulence, they were not interested in the idea of going with Him to Dvaraka. They wanted to take Him back to Vrndavana and enjoy His company.
This incident of the gopis inviting Krishna back to Vrindavana is the Ratha Yatra festival.
Externally, Rathayatra is spectacular colorful and entertaining. Yet the Gaudiya Vaisnavas, the followers of Lord Caitanya, they see in the Festival of the Chariots much more than just a happy event. The pulling of the cart by the Lord's devotees symbolizes the attempt of the Vrajavasis, especially Srimate Radharani and the gopis, to bring Krsna, Balarama, and Subhadra back to Vrndavana.
Vrndavana can also represent the heart of Krsna's devotee. Sri Caitanya Mahaprabhu prayed to Lord Krsna, "For most people the mind and heart are one, but because My mind is never separated from Vrndavana, I consider My mind and Vrndavana to be one. My mind is already Vrndavana, and since You like Vrndavana, will You please place Your lotus feet there? I would deem that Your full mercy" (Cc. Madhya 13.137).
For the devotees of Lord Jagannatha who follow in the footsteps of Lord Caitanya, pulling the Rathayatra cart is like pulling their worshipable Lord, Jagannatha or Krsna, into their heart.