Recently, photonic skyrmion as a topological nontrivial structure has attracted widely research attention. Due to their ultracompact size, high stability, and diversity of topologies, photonic skyrmions have potential value in applications of high-resolution polarization imaging, high-density optical information storage, and high-precision displacement sensing. In this paper, the fundamental mechanisms and the excitation and detection methods of photonic skyrmion are introduced, and the domestic and foreign state-of-the-art studies on the photonic skyrmion in different optical systems are summarized. In view of the deep-subwavelength features of the photonic skyrmion, the recent research progress of the applications of photonic skyrmions is also reviewed, and its future development is analyzed and prospected.