MmWave (millimeter wave) Frequency Modulated Continuous Waves (FMCW) RADARs are sensors based on frequency-modulated electromagnetic which see their environment in 3D at a long-range. The recent introduction of millimeter-wave RADARs with frequencies from 60 GHz to 300 GHz has broadened their potential applications thanks to their improved accuracy in angle, range, and velocity. MmWave FMCW RADARs have better resolution and accuracy than narrowband and ultra-wideband (UWB) RADARs. In comparison with cameras and LiDARs, they possess several strong advantages such as long-range perception, robustness to lightning, and weather conditions while being cheaper. However, their noisy and lower-density outputs even compared to other technologies of RADARs, and their ability to measure the targets' velocities require specific algorithms tailored for them. Working principles of mmWave FMCW RADARs are presented as well as the separate ways to represent data and their applications. This paper describes algorithms and applications adapted or developed for these sensors in automotive applications. Finally, current challenges and directions for future works are presented.