Vedic is the earliest form of Sanskrit, being the language in
which the Vedas were written. The oldest text is the Rig Veda
(Rg Veda), which seems to date from a little before 1000 BCE. It
was spoken in north-western India, before the Aryan people had
spread far and wide over the Indian subcontinent. (However, see
Aryan invasion theory for doubts over this traditional dating
for the migration.)  Vedic Sanskrit differs from Classical
Sankrit, the prestige language codified by the grammarian Panini
at an unknown date, perhaps around 300 BCE. From Panini's time
Sanskrit was only a literary/theological/philosophical medium,
not a living language of the people: by then they spoke Prakrit
in the various dialects that gave rise to modern Indian
languages. Prakrits are phonetically much simplified compared to
their ancestral Sanskrit; however, Vedic Sanskrit and Classical
Sanskrit do not differ greatly.  Some scholars insist that Vedic
is not a form of Sanskrit, and that 'Vedic Sanskrit' is a
contradiction in terms.