Rigveda
The Rigveda Samhita is the oldest Veda. It is a collection of 1,028 Sanskrit hymns and 10,600 verses. The hymns are dedicated to Rigvedic deities. More than half the hymns are dedicated to Indra (250 hymns), Agni has 200 hymns, and Soma over 100 hymns.
Samaveda
The Samaveda Samhita consists of 1549 stanzas. The Samaveda Samhita comprises two major parts. The first part include four gāna (melody collections) and the second part composed of three ārcika (verse books). A melody in the gāna corresponds to a verse in the arcika.
Yajurveda
The Yajurveda Samhita consists of mantras. The early part of Yajurveda Samhita are in prose. The Yajur Veda has been the primary source of information about sacrifices during Vedic times and associated rituals. There are two major groups of texts in this Veda: the "Black" (Krishna) un-arranged collection and the "White" (Shukla) well-arranged section.
Atharvaveda
The Artharvaveda Samhita was composed by Atharvan and Angirasa poets. It has 760 hymns. Most of the verses are metrical, but some sections are in prose. The Atharvaveda is a comparatively late extension of the "Three Vedas". The Atharva Veda has been the primary source for information about Vedic culture, the customs and beliefs, the aspirations and frustrations of everyday Vedic life, as well as those associated with kings and governance.
What's the Origin of the Vedas and its inception?
Lord Brahma after a day full of creation, was tired and fell asleep. In his sleep, he was reciting the knowledge in the four Vedas from his four heads. Asura Madhu-Kaitabha started absorbing the knowledge in the Vedas. He then hid deep inside the ocean crater. Lord Vishnu knew this and was worried, if the Vedas were to be hid by the asura, the knowledge could not be passed on for the betterment of creation in the subsequent Yugas.
As Preserver, Lord took his Matsya avatar. A god-loving, honest and just king, King Manu, as part of his daily routine went to the river for his prayers at dawn. He took some water in his cratered palms to offer obeisance to Lord Vishnu. Right then, he heard a voice ‘O great king! Please do not put me back in the river. The bigger fishes would eat me!’ Manu looked closely to find a tiny fish floating in the water cupped by his palms. Kind King Manu put the fish in his ‘Kamandala’ (small jug carried by sages) and went about his daily duties. He woke up next morning to find a big fish staring at him from the top of the 'Kamandala'. The tiny fish had grown bigger and the ‘Kamandala’ was now too small for it.

On the seventh day, after torrential rains and huge floods, the giant fish came to rescue Manu and all of creation. Vasuki was tied to the huge boat on one end, the other end was fastened to the horn atop the giant fish's head. Then the fish guided the boat over the waters to the shores atop Mount Himavan. The rescued flora and fauna started life afresh with the gift of the Three Vedas! Atharva Veda was to be introduced later by sage Atharvan and Angirasa (rebirth of the Madhu-Kaitabha as sages)