The author has given a brief introduction of an all-time great Mathematician Srinivasa Ramanujan, the man who reshaped twentieth-century mathematics with his various contributions in several mathematical domains, including Mathematical analysis, Infinite series, Continued fractions, Number theory and Game theory.He has established new general theorems for the explicit evaluations of Ramanujan's remarkable product of theta function and their new explicit assessment.He has also established several new P - Q eta-function identities which were obtained, leading to several new modular relations...