Vedic Sanskrut :

Vedic Sanskrut is the language of the Vedas, a large collection of hymns, incantations (Samhitas), theological discussions, and religio-philosophical discussions (Brahmanas, Upanishads) which are the earliest religious texts of the Hindu religion.

Classical Sanskrut :

The Vedic form survived until the middle of the first millennium BC. Around this time, as Sanskrut made the transition from a first language to a second language of religion and learning, the Classical period began.It is a significant form of post-Vedic Sanskrut and is found in the Sanskrut of the Hindu Epics Ramayana and Mahabharata. There have been "prakritisms" (borrowings from common speech) in this form of Sanskrut.

Classical Sanskrut became fixed with the grammar of Panini (roughly 500 BC), and remains in use as a learned language until the present day.