Rigveda is considered the first Veda. Rigveda contains a collection of mantras in praise of various gods and goddesses. The mantras of Rig Veda originated at different times. Some mantras are ancient and some are modern. Therefore, the subject of their description is also different. Keeping in mind the subject matter of the mantras, they were arranged in different divisions. The five branches of Rigveda have been mentioned by Shaunaka in an appendix called Charanvyuh. The five branches of Rigveda are Shakal, Vashkal, Ashvalayan, Sankhyayan, Mandukayan. Rigveda has 10,600 mantras which are divided into 1028 suktas, 1028 suktas are divided into 85 anuvakas and 85 anuvakas are divided into 10 mandalas. Rig Veda is considered to be the first Veda and the first mantra of the first Veda is called "Hotaram Ratnadhatamam" .
ॐ अग्निमीळे पुरोहितं यज्ञस्य देवमृत्विजम् . होतारं रत्नधातमम्
The meaning of this mantra is that I praise fire. One who is the priest of the Yagya, endowed with charitable qualities, the one who calls the gods in the Yagya and wears the gems that are the fruits of the Yagya.
O fire god, I bow to you
Yes, you are the priest of the yagya.
you are means of sacrifice through daan
you are the invocation of the gods
Yagya fruit should also be a gem bearer
O fire god, I bow to you