Several cosmological phenomena occurring at various epochs generate a stochastic gravitational wave background (GWB). One of the fundamental mechanisms is the generation of GWB from the primordial fluctuations in the early universe. This simple and rudimentary phenomenon encodes into GWB the information about the initial conditions of cosmological perturbations that evolve into the structure of the current universe. Given the signal of stochastic GWB observed by the International Pulsar Timing Array collaboration and the forecasts of upcoming observatories such as Einstein Telescope probing GWB at different frequencies, it becomes imperative to analyse the generation of primordial GWB and arrive at precise predictions on its properties, such as its amplitude, spectral shape, polarizations, structure of correlations and anisotropies. 

In this talk, I shall discuss such analyses that transform GWB into a novel probe of precision cosmology. Specifically, I shall demonstrate how GWB shall serve to probe primordial non-Gaussianity, to trace the generation of cosmic magnetic fields and to test fundamental symmetries such as parity. I shall present how GWB can complement the existing datasets of cosmic microwave background and large scale structure in levying precise constraints on certain cosmological parameters. I shall conclude with a summary of my recent results and outlook of ongoing projects in this regard.