The future of wireless communication looks promising, thanks to its various applications and the demanding needs of upcoming 6th generation (6G) and subsequent wireless networks. Since the advent of modern wireless technology, the propagation channel has been seen as an unpredictable factor in the communication process that degraded the quality of the received signal. With the recent emergence of reconfigurable intelligent surfaces (RIS), network providers can now control the way radio waves are scattered, reflected, and refracted, improving the performance of wireless communication systems. RIS provide a potential solution for creating a software-configurable smart radio environment. By controlling the communication environment, the quality of service and the spectrum efficiency will be increased. According to its features, RIS is one of the most important enablers for 6G and promising candidate in the future of wireless networks. This paper seeks to offer a thorough overview of RIS, while also discussing the key differences from relays and highlighting the most pressing open research challenges to address.