Vedas are the first words of God revealed to mankind through highly accomplished sages and Rishis of that era.
Before Vedas, existed Dharma, “Your right to do what is just and right and not what was destined”. Based on inherent Dharma that existed in human beings and also all living beings, human beings conducted themselves amongst each other.
For this very reason Hinduism is also called Sanatana Dharma, a Dharma that exists since times immemorial, an eternal Dharma.
Ever since mankind came into being existed Sanatana Dharma. The whole layout of Hinduism can be depicted by following example:
Initially came, tree of Dharma when no religion existed on mother earth. During those times it was only Dharma based on which human beings dealt with each other. That tree of Dharma grew further. If we cut the stem of tree of Dharma we find four compartments and four Vedas advent on mother earth… Rig Veda, Sama Veda, Yajur Veda and Atharva Veda.
All the four Vedas are voluminous documents beyond reach of commoners, masses. The tree of Dharma grew further and advent the first avatar Lord Krishna. The entire gist of Vedas necessary for mankind was reproduced by Lord Krishna in form of Bhagavad Gita. Only the important teachings necessitated were incorporated in Bhagavad Gita.
The teachings contained in Bhagavad Gita were simpler easier to understand. With coming of Bhagavad Gita, the need to indulge in Vedas ceased to exist. The tree of Dharma grew further and developed its first branch. Lord Mahavira, 24th Tirthankara of Jainism manifest. About 77 years later to Mahavira the tree of Dharma developed another branch and advent Gautama Buddha. Then Jesus Christ followed by Prophet Mohammed.
The analogy of tree of Dharma explains the fundamentals of life contained in Hinduism. Initially came Dharma followed by Vedas, then came teachings of Bhagavad Gita followed by enlightened ones like Mahavira, Gautama Buddha, Jesus Christ and Prophet Mohammed. Between Vedas and Bhagavad Gita all the Upanishads evolved. Various Sages and Rishis who were adept in spiritual wisdom categorized different fields of spirituality into independent Upanishads. Total Upanishads exceed 200 whereas there were 11 primary Upanishads.
There is no doubt about the fact that Hinduism, Sanatana Dharma is not only the oldest religion of the world but also the best and would continue to do so.
All Vedas, Upanishads, Itihasas, Puranas and Agamas collectively form part of Hinduism.