The microstrip-line feed is the simplest feed, where the DR is directly placed on the transmission line which is printed on the substrate. It has been shown in [27] that the overlap distance between the DR and the microstrip-line feed controls the coupling strength and the specific mode that is excited by the transmission line. As the overlap distance is shorter than one quarter of a dielectric wavelength of the resonance frequency, the strongest coupling happens. The main limitation of the microstrip-line feed is that the feeding line is not isolated from the DR and may disturb the radiation performance of the DRA. Moreover, when the DR is placed directly on the top of a microstrip-line feed, an undesired air gap is formed between the DR and the substrate. A single-feed configuration suffers from a narrow AR bandwidth and severely restricts the applications of DRA. A dual or multiple feed configuration can also be used to excite CP waves. A dual or multiple feed configuration is based on the sequential phase (SP) rotation technique to create CP radiation with low cross-polarization and a higher AR bandwidth. This configuration requires a power divider to create CP radiation and the feed points should be orthogonal to each other with a 90\({}^{\circ}\) phase difference [28]. Typically, a CP DRA with dual or multiple feeds has a wide AR bandwidth but has a complicated design, bulky size, and high manufacturing cost as compared to single-feed CP techniques. Review papers on CP DRAs exist in the literature [29; 30; 31]. However, the authors in [29] summarized their general thoughts about DRA, the advantages, and a comparison of the recent techniques used to obtain wideband CP DRAs. Whereas, in [30], the authors focused on the summarization of different techniques to generate a dual-band CP DRA only. Moreover, in [31], the authors summarized the basic concept of the CP mechanism for DRA in addition to the methods that can be used to obtain circular polarization in DRA. Previous review papers published in [29; 30; 31] summarized the methods of generating circular polarization in DRA and the advantages in general. However, a detailed comparison in terms of efficiency, modes, and applications using DRA are not covered by any other previous papers to the best of our knowledge. Therefore, our work not only includes a comprehensive review of different methods of producing circular polarization waves and the advantages, but additionally lists several applications using DRA and its important parameters. The paper is organized as follows: Section 2 explains the theory of dielectric resonator antenna. This section also explains the different methods of single- and dual-feed or multiple-feed DRAs to achieve CP. Moreover, a brief comparison in terms of resonant frequency, bandwidth, gain, efficiency, and mode is presented in Section 2. In Section 3, the performance of several multiple-input-multiple-output (MIMO) CP DRA is accessed in terms of the reflection coefficient, CP bandwidth, feed type, gain, and isolation. Section 4 comprehensively elaborates on a millimeter-wave CP DRA. Various applications of DRA are listed in Section 5. Lastly, the conclusion of this paper is presented in Section 6.