Vedas are earliest Literature recorded in Human History.

This,along with the other Three Vedas,Yajur( Sukla and Krishna),Sama and Atharva forms the basic reference authority on everything related to Hinduism

The words of the Vedas are final

Each Veda has four parts.

They are,

Samhitas,

• The Samhitas consists of hymns of praise of Gods
• The Brahmanas are rituals and prayers to guide the priests in their duties.
• The Aranyakas concern worship and meditation.
• The Upanishads consist of the mystical and philosophical teachings of Hinduism.

This corresponds to the Four Stations of Life

Brahmacharya,the life of celibacy and studentship,Samhitas)

Gruhastha,Married Life,( Brahmanas)

Vanaprastha,Retired Life,when one having completed his family responsibilities meditates on the Reality of Brahman,preferably in a forest.(Aranyaka) and

Sanyasin,the State of total renunciation,seeking answers to Life and Realizing Self( Upanishad)

Though each stage of Life is called Asrama,Station of Tranquility is connected one aspect of  the Vedas,there is no bar in learning all the components of the Vedas,though one is advised to practice what is meant for his Station,Asrama.

Of these Four Vedas,the Rig Veda is the oldest.

The Vedas were compiled by Seers,called Rishis.

The Vedas are meant to be heard and learnt.

They were transmitted orally,never in a written form,though they were written on Palm leaves.

These Rishis are numerous.

Each Mantra has a Rishi.

So there are many Rishis who complied the Vedas.

But the earliest,first Rishis who performed the Duties of Priests are Ten.

These Families represent the First Rishis of the Vedas.

They are,

1. ANgirases,
2. BhRgus,
3. ViSvAmitras,
4. VasiSThas,
5. Agastyas,
6. KaSyapas 
7. Atris,
8. Kevala-ANgirases (KaNvas in the Rigveda)
9. Kevala-BhRgus (GRtsamadas in the Rigveda).
10.  Bharatas.*   

* This family does not figure as a separate family in later priestly traditions, which place kings who became RSis among either the ANgirases or the BhRgus.