In fifth generation wireless networks, the escalating teletraffic and energy consumption has necessitated the development of green communication techniques in order to further enhance both the system’s spectral efficiency and energy efficiency. In the past few years, the novel index modulation (IM) has emerged as a promising technology that is widely employed in wireless communications. In this paper, we present a survey on IM in order to provide the readers with a better understanding of its principles, advantages, and potential applications. We start with a comprehensive literature review, where the concept of IM is introduced, and various existing IM schemes are classified according to their signal domains, including the frequency domain, spatial domain, time domain and channel domain. Then the principles of different IM-aided systems are detailed, where the transceiver design is illustrated, followed by descriptions of typical systems and corresponding performance evaluation. A range of challenges and open issues on IM are discussed before we conclude this survey.