Black-hole binaries (BHBs) are X-ray binary systems containing a compact object with a mass greater than 3 solar masses, confirmed to be a black hole. These systems are studied to understand black hole physics, accretion processes, and the effects of strong gravity. The review discusses the X-ray properties of 20 BHBs, 17 of which are transient systems. Observations using the Rossi X-ray Timing Explorer (RXTE) have revealed complex behavior patterns in these systems, including three distinct X-ray states: thermal, hard, and steep power law (SPL). These states are characterized by different spectral and timing properties, such as the dominance of thermal or nonthermal emission, the presence of quasi-periodic oscillations (QPOs), and the geometry of the accretion disk. The review also highlights the importance of X-ray observations in understanding the interaction between black holes and their environments, including relativistic jets and the measurement of black hole spin. The study emphasizes the role of X-ray timing and spectral analyses in probing strong gravity and testing general relativity. The review concludes that X-ray states are important for understanding BHB behavior, but they are not simply a function of source luminosity. The analysis of X-ray QPOs and their correlations with spectral properties provides insights into the physical processes governing accretion and jet formation in BHBs.Black-hole binaries (BHBs) are X-ray binary systems containing a compact object with a mass greater than 3 solar masses, confirmed to be a black hole. These systems are studied to understand black hole physics, accretion processes, and the effects of strong gravity. The review discusses the X-ray properties of 20 BHBs, 17 of which are transient systems. Observations using the Rossi X-ray Timing Explorer (RXTE) have revealed complex behavior patterns in these systems, including three distinct X-ray states: thermal, hard, and steep power law (SPL). These states are characterized by different spectral and timing properties, such as the dominance of thermal or nonthermal emission, the presence of quasi-periodic oscillations (QPOs), and the geometry of the accretion disk. The review also highlights the importance of X-ray observations in understanding the interaction between black holes and their environments, including relativistic jets and the measurement of black hole spin. The study emphasizes the role of X-ray timing and spectral analyses in probing strong gravity and testing general relativity. The review concludes that X-ray states are important for understanding BHB behavior, but they are not simply a function of source luminosity. The analysis of X-ray QPOs and their correlations with spectral properties provides insights into the physical processes governing accretion and jet formation in BHBs.