According to the generation mechanism of electromagnetic (EM) phase, electromagnetic metasurfaces can be divided into resonance-based metasurfaces using resonance response of microstructures and geometric-phase metasurfaces using anisotropic response of microstructures. In comparison with the resonance-based metasurfaces, geometric-phase metasurfaces have attracted much attention in recent years because of their non-dispersion, polarization dependence, and easy fabrication. This study presents an overview of the development of geometric-phase metasurfaces from the principle and method of their free modulation of EM waves to their extraordinary wavefront manipulation abilities in both the far- and near-field regions. Finally, we also present three typical applications enabled by geometric-phase metasurfaces, including highly efficient meta-hologram, vortex beam generator/detector, and flat achromatic metalens.