In Western scholarship it has been vogue to ignore the authoritative statements that the Vedas make about themselves & to instead speculate who, when and why composed them.
asya mahato bhUtasya niHzvasitam etad yad
Rgvedo yajurvedaH sAmavedo 'tharvAGgirasa
itihAsaH purANaM vidyA upaniSadaH zlokAH sUtrANy
AnuvyAkhyAnAn yasyaiva itAni niHzvasitAni
vedo nArAyaNa sAksAt svayambhUr iti zuzruma
“The Vedas are directly the Supreme Personality of Godhead, Narayana, and are self-born."
The same reference also explains the purpose of the Vedas:
veda-pranihito dharmo hy adharmas tad viparyayaH
"That which is prescribed in the Vedas constitutes dharma, the religious principles, and the opposite of that is Adharmic."
However,the Upanisads are accepted as belonging to the Vedas, infact,they are taken to be the actual explanations of the Vedas.
Below text (Bh.P. 11.21.35-42) gives an esoteric explanation of the Vedic path.
veda brahmatma-visayas tri-kanda-visaya ime
paroksa-vada rsayah paroksa mama ca priyam
sabda-brahma su-durbodha pranendriya-mano-mayam
ananta-para gambhira durvigahya samudra-vat
mayopabrmhita bhumna brahmanananta-saktina
bhutesu ghosa-rupena visesurneva laksyate
akasad ghosavan prano manasa sparsa-rupina
chando-mayo 'mrta-mayah sahasra-padavi prabhuh
vicitra-bhasa-vitata chandobhis catur-uttaraih
ananta-para brhati srjaty aksipate svayam
gayatry usnig anustup ca brhati panktir eva ca
tristub jagaty aticchando hy atyasty-atijagad-virat
ki vidhatte kim acaste kim anudya vikalpayet
ity asya hrdaya loke nanyo mad veda kascana
Who is the bull of the chants, possessing all forms, who from the immortal chants was born, may that Indra deliver me with wisdom. (Taittiriya Up. 1.3.1)
Dirghatamas states in the Rg-Veda:
The sacred syllable of the chant in the supreme ether in which all the gods reside, he who does not know that, what can he do with the Veda? (I.164.39)
"That sacred syllable on which the Vedas rest is om."
In the edition that I’m using the verse appears as 12.10 and is said to be identical with Rg-Veda IV.58.3. The Sanskrit is as follows:
tridha baddho vrsabho roraviti maho devo martyan avivesa
The verse in question may be interpreted as a description of the sacred syllable om, as a list of the various flexions of speech and as an example of the Vedic sacrifice itself.
In modern times the Vedic literature has been examined and translated by Western scholars such as Mueller, Wilson, Keith, Griffith and Bergaine.
The Rg-Veda is said to have been composed in the Punjab region of northwest India as the first step of this invasion. These are ideas used to interpret the text.
The Aryan invasion is a myth invented by Western scholars in order to discredit the original Vedic civilization.
A modern scholar has written:
Also included under the designation Vedic are the Sutras, Upanisads, and Aranyakas. The Sutras are manuals for teaching in ritual, philosophy, grammar and so on.
The Aranyakas, literally 'forest-born', are a class of philosophical writings which are closely connected with the Brahmanas.
Besides the scriptures mentioned above there are also the six Vedangas, literally 'limbs of the Vedas'.
3)Vyakarana, linguistic analysis or grammar, represented by Panini's celebrated Sutra.
4)Nirukta, explanation of difficult Vedic words.
(1) vaisesika, propounded by Kanada Rsi
(3) yoga or mysticism, propounded by Patanjali Rsi
(4) the philosophy of sankhya, propounded by Kapila Rsi
(5) the philosophy of karma-mimansa, propounded by Jaimini Rsi
ucchistaj jajnire sarve divi deva divi-sritah
"The Rg, Sama, Yajur, and Atharva Vedas appeared from the Supreme Lord along with the Puranas and all the demigods residing in the heavenly planets." (Atharva Veda 11.7.24)
tam itihasas ca puranam ca gathas ca narasamsis canuvyacalan
itihasasya ca vai sa puranasya ca gathanam ca narasamsinam ca priyam dhama bhavati ya evam veda.
(Atharva Veda 15.6.10-12) meaning 👇🏼
sopanisatkah setihasah sanvakhyatah sa-puranah.
"In this way all the Vedas were manifested along with the kalpas, rahasyas,Brahmanas,Upanisads, Itihasas, anvakhyatas and Puranas" (Gopatha Brahmana,Purva 2.10).
"Indeed Rg, Yajur, Sama, and Atharva are the names of the four Vedas. The Itihasas and Puranas are the fifth Veda" (Chandogya Up. 7.1.4).
itihasa-puranani sa bhaved veda-para-gah
"One who thoroughly studies the Vedas along with their six limbs and the Itihasas and Puranas becomes a true knower of the Vedas" (Vyasa-smrti 4.45)