<p>Flexoelectricity is a physical phenomenon wherein electrical polarization is induced by a strain gradient. This effect is markedly enhanced in ferroelectric materials, owing to their large dielectric effect. In recent years, with the rapid development of micro- and nanotechnology, flexoelectricity has garnered growing interest. This article provides a comprehensive overview of classical theories and recent advances in flexoelectricity, with a primary focus on ferroelectric materials. This work reviews the advantages and disadvantages of various characterization techniques in flexoelectricity, calculational models for flexoelectric coefficients, enhancement mechanisms in different ferroelectric materials and explores the applications in devices. Finally, future research directions are outlined, with the goal of providing valuable insights for the fundamental science of flexoelectricity and high-performance practical devices.</p>