Abstract—Intelligent Reflecting Surface (IRS) is a promising technology for enhancing the coverage of millimeter wave (mmWave) based future wireless communication systems. Severe path loss and high directivity make mmWave transmission vulnerable to blockage. To overcome these issues, Intelligent Reflecting Surface (IRS) is introduced as a revolutionizing technology to provide better communication with the help of a virtual line-of-sight (LOS) link to bypass obstacles between transceivers through intelligent reflections. Significant performance improvement is achieved by smartly reconfiguring the wireless propagation environment using low-cost passive reflecting elements integrated on a planar surface. In this paper, we provide a survey of the IRS technology, its applications in mmWave wireless communication scenario, advantages over existing technologies, key design challenges, hardware architecture and the practical constraints while deployment. Furthermore, we highlight the relevant directions in future work.