The refractive index of a material determines the fundamental properties of light propagating in it. Developing novel materials with various refractive indices is an important research topic in optics. Among many new optical materials, the zero refractive index materials have attracted much attention due to their unique electromagnetic properties. Zero refractive index requires that both the permittivity and the permeability are zero. The effective zero refractive index is usually achieved based on the metal-dielectric composite structures or photonic crystals. However, the zero refractive index of the artificial materials is a macroscopic effect, and the refractive index is not zero at the microscopic scale. At the same time, researchers are also interested in the near-zero refractive index materials, which have similar electromagnetic properties to that of the zero-index materials. In this kind of material, the real parts of the permittivity of some materials are zero at specific wavelengths and are referred to as Epsilon-near-zero (ENZ) materials. The permeability is usually close to 1. When light propagates in an ENZ material, the phase velocity exceeds the speed of light in a vacuum. Therefore, the propagation phase is small, which can be used for electric field tunneling, electric field shielding, and perfect wave bending in waveguides. ENZ materials can be used to localize the electric field of lincident light, enabling the enhancement of nonlinear optical responses and light-matter interactions. Transparent Conductive Oxides (TCO), such as the indium tin oxide, aluminum-doped indium oxide, and indium-doped cadmium oxide, have near-zero permittivities in the near-infrared spectral region and have excellent electro-optic tunability, and have received extensive attentions in recent years. TCO have great application potentials in the fields of electro-optical modulation, nonlinear optical frequency conversion, and all-optical modulation, thus representing an important material platform for developing novel nonlinear optical devices. In this paper, the physical principles and applications of light-matter interactions in the ENZ materials are reviewed from the view points of both linear and nonlinear light-matter interactions. In the part of linear light-matter interaction, this paper discuss the following contents: ENZ materials and their optical properties; optoelectronic properties and dielectric constants of the TCO; preparation methods of the TCO; ENZ mode in ultra-thin film and its optical properties; electro-optic modulation scheme and carrier modulation mechanism of TCO. In the part of nonlinear light-matter interaction, this paper summarize the progress on the following topics: the enhancement mechanism of nonlinear optical response in ENZ materials; the nonlinear refractive index of the ENZ materials and the physical model, and the recent progress on all-optical modulation; the second harmonic generation in ENZ materials, high harmonic generation, generation of supercontinuum and terahertz waves in the ENZ materials; phase conjunction and negative refraction phenomena with the ENZ materials. Finally, the research trends of the ENZ materials are overlooked, and the future research directions and applications in the fileds of ENZ materials are prospected.