Understanding the temporal and spectral variations in X-ray binaries is extremely important in order to explore the various processes in accretion disk i.e. production of soft X-ray and hard X-rays, Comptonizing region, reflection component, origin of jet, ejection mechanisms etc.. These sources show astounding variability on a time scale of microsecond to days in a broad spectral domain of 0.1 - 200 keV and any profound knowledge of these phenomenon can potentially be invoked to understand the spectro-temporal activity in AGNs. I will discuss various statistical methods and procedures often used to study X-ray binaries in order to probe the X-ray emitting region/regions in accretion disk, considered to be occurring close to the compact object. I will discuss, how the magnitude of cross correlation function, autocorrelation function, power density spectrum and Fourier time lags between soft and hard X-ray shall constrain the Comptonization region in X-ray binaries, whose geometry is still a matter of debate. I will briefly elaborate on few primary results unveiled by Astrosat and RXTE connected to the X-ray binaries. I will show a ongoing study using RXTE and Nustar data of a neutron star source GX 17+2 emitting close to the Eddington luminosity and constrain the X-ray production mechanism.