Who is Sanjaya from The Bhagavad Gita and what is their importance?

Sanjaya is either the title or the name of one character. Sanjaya is not a character in the story. However, his role is that of the presenter. He is the messenger to the listening audience of one. He is listed as the one speaking on a few occasions during the book. There is no certainty whether this was an actual messenger or if this was a story teller or if this was a theatrical contrivance.