Indium-tin-oxide (ITO) thin film is one of the indispensable materials for advanced technologies. Due to its unique characteristics such as high transparency to the visible light, low electric resistivity, excellent adhesion to the substrate, and chemical stability, the ITO thin film has been reported possessing an important role in opto-electronic applications. Here, a brief review giving description of the development, application, preparation method, and characterization of ITO thin film is present.