The Vedas are the oldest knowledge known to man which existed before creation (before 155.522 trillion years ago) and the oldest written documents on the planet. The Vedas constitute Dharma (religious principles) and reveal the Supreme person as Lord Krishna who has a spiritual form, and the living entities are pure spirit souls, entangled in the material world due to identifying the self as matter (bodily designations) rather than the eternal soul. The Bhagavad-Gita which was spoken 5000 years ago by the Supreme person (Lord Krishna) is the essence of all the Vedas.
The Upanishads are the end part of the Vedas which explain in detail the philosophic principles of the Vedas and reveal spiritual truths in depth. They give satisfactory answers to the profound questions of life: Who am I?; What is this universe?; Where do we come from?; Where do we go after this life?; How do we attain immortality, eternal freedom, perfection, eternal bliss, an eternal body, eternal peace?
The past-times and teachings of God, Lord Ram (an incarnation of Lord Krishna). The essence of Ramayan is that there is a war and the side with Lord Ram wins over the other side with the evil person called Ravana and his followers. The same happened in the Mahabharat war. The side with Lord Krishna wins. One should learn from this and surrender unto Lord Krishna, the only savior and proven God.
Historical events that took place in the World 5000 years ago, the past-times of God (Lord Krishna). It contains many areas of charity, generosity, military science, and the science of God is included in the Bhagavad Gita which is spoken by Lord Krishna to Arjuna in public.
The Puranas are supplementary explanations of the Vedas intended for different people according to their mentality/consciousness/intelligence. All people cannot understand everything equally. The Puranas are classified into three modes with six in each category and different people will understand the category of Puranas based on their own qualification. Some people are in the mode of goodness, some in passion, and others are in ignorance.
There are many other Vedic scriptures including: Vedanta Sutras, Brahma Sutras, Yoga Sutras (Physical health), Ayurveda (Medicine), Dhanurveda Veda (Military science), Gandharva Veda (Science of music and arts), Arthashastra Veda (Science of politics and economics), Manu Sutras, Devi Purana, Ganesha Purana, Vayu Purana, over 100 other Upanishads, other Puranas, 6 Vedangas, 20 Dharma Sastras, 18 Upapuranas, 18 Vidyas, 641.kalas, 64 Tantras and so on..