The Rig Ved ("Wisdom of the Verses") is a collection of inspired songs or hymns which probably did not reach its final form until about the 6th century BC. It contains the earliest form of all Sanskrit Mantra that date back to 1,500 BC - 1,000 BC but the earliest parts of which may go back as far as 1,300 BC - approximately the fall of Myeenean Greece in Europe. Some scholars date the Rig Ved as early as 12,000 BC - 4,000 BC.

Rig Ved Sanhitaa is the oldest collection of Sookt. Though there were 21 Shaakhaa in these, only five are available now.
These are - (1) Shaakal,  (2) Baashkal,  (3) Aashwalaayan,  (4) Shaankhaayan,  and  (5) Maandookeya.

There are 10, 552 Mantra in the 8 Ashtak and 64 Adhyaaya. There are 10 Mandal, 85 Anuvaak.
The topics dealt with concerns deities like Agni, Indra, Varun etc. It also deals with the origin of universe and the nature of human beings (including secular subjects like marriages, wars etc)
Although Sagunopaasanaa is predominant, it teaches monotheism (Ek devataa vaad) .and not polytheism.

The Rig Ved has the following:
(1) Aitareya and Kausheetikee Braahman,
(2) Aitareya and Shaankhaayan Aaranyak,
(3) Aitareya and Kausheetikee Upanishad.

It is collection of 1,028 hymns or "Sookt", not all directly religious and dedicated to 33 different gods, but mostly to Indra, Agni and Som Dev. These 10,589 (or 10,552) verses of the Rig Ved are divided into 10 Mandal or books, of which books 2-7 are the core of the work. Its main function was to provide orders of worship for priests responsible for sacrifices which were very common to the religion of Indo-Aryan. Two further texts that began to be created towards the end of the period in which Rig Ved was being written down - the Yajur Ved and the Saam Ved, also served the same purpose. The Atharv Ved is largely a collection of magic spells.

There is a striking similarity between the language of he Rig Ved and Zoroastrian's Holy Bible, the Zend Avesta.

The 1st Mandal consists of 181 Sookt and   2006 Mantra (some say 191)
The 2nd Mandal consists of 43 Sookt and    429 Mantra
The 3rd Mandal consists of 62 Sookt and     617 Mantra
The 4th Mandal consists of 58 Sookt and     589 Mantra
The 5th Mandal consists of 87 Sukt and       727 Mantra
The 6th Mandal consists of 75 Sookt and     765 Mantra
The 7th Mandal consists of 104 Sookt and    841 Mantra
The 8th Mandal consists of 103 Sookt and  1,716 Mantra
The 9th Mandal consists of 114 Sookt and   1,108 Mantra
The 10th Mandal consists of 181 Sookt and 1,754 Mantra   (some say 191)
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                                         1,008 Sookt  and   10,552 Mantra

There seems to be some incoherency in these numbers. The numbers in bracket are from a site on Web. This increases the number by 20 Sookt, means a total of 1028 Sookt. This number coincides with the number written above in the beginning.

These hymns have been written by many authors or seers called 'Rishi', such as Maharshi Atri, Maharshi Kanv, Maharshi Vashisth, Maharshi Vishwaamitra, Maharshi Jamadagni, Maharshi Gotam and Rishi Bhaaradwaaj. They are first of all described by Kaatyaayan Rishi in the Rig Ved Sarvaanukramaani. A uniformity is noticed from the 2nd to 7th Mandal. It seems that one Rishi's dynasty was related to one Mandal. These Mandal are related to the heritage of Gritsamad, Vaam Dev, Atri, Vishwaamitra, Bharadwaaj and Vashishth Rishi. Among them also, the Sookt follow a certain order. 9th Mandal is about Som gods. Rishi of the 2nd and 9th Mandal are different than the Rishi of 1st and 10th Mandal. The books are arranged according to the number of hymns they possess. The main ritual they refer to is sacrifice.

Its main Mantra is Gayatri Mantra addressed to the Sun god.

Vishwaamitra Jee is believed to be the author of most of the Mandal 3 of Rig Ved, including Gaayatree Mantra. According to Puraan, only 24 Rishi understood the meaning of the Gaayatree Mantra fully and thus wielded the whole power of it - sage Vishwaamitra was the first and sage Yaagyavalkya was the last.

The religion of the Rig Ved is a polytheism consisting of divinities associated with Prakriti - Aakaash, Vaayu, Prithvi, Jal and Agni. Many of the most important Vaidik gods are almost forgotten today, Indra was the great war god of the Aarya but later became mainly a rain god. Varun, the guardian of the cosmic order, is rarely remembered today, whereas Soorya, the Sun god, and Agni, the god of fire and sacrifice, are still honored. Rig Ved intones that since all are embodiments of the Divinity, all human beings are one. Human beings should trot the path of Satya and Rit - the truth. See also  Devtaa in Rig Ved

Rig Ved 10.129 says - It is believed 2 x 7 = 14 Earth (14 Lok)

Rig Ved Sookt
According to Bhavishya Puraan, 3/22 - "King Praanshu satisfied Soorya Dev with Rig Ved Sookt".

It is believed that who follow Rig Ved, means Rig Vedik Braahman, do not do Hom (Yagya or Fire sacrifice). Hom is not necessary for them since they are believed to be having Karaagnihotra - means having Agnihotra in their palms. that is why they do not perform Homam either in Upanayan Sanskaar or Vivaah ceremonies. Hom is not performed in Shraaddh also. Other Pandit well versed in A-par Karm and other ceremonies.