Copper oxide superconductors and iron-based superconductors are two important families of high temperature superconductors. Their high-temperature superconductivity mechanism is a long-standing issue and still in hot debate in the field of condensed matter physics. The extensive and in-depth exploration of iron-based superconductors and their comparative study with copper oxide high-temperature superconductors are of great significance for the development of new quantum theory, the solution of high-temperature superconducting mechanism, the exploration of new superconductors and practical applications of superconductors. The macroscopic properties of materials are determined by their microscopic electronic structure. Revealing the microscopic electronic structure of high temperature superconductors is fundamental for understanding high temperature superconductivity. Angle-resolved photoelectron spectroscopy, due to its unique simultaneous energy, momentum and even spin resolving ability, has become the most direct and powerful experimental tool for detecting the microscopic electronic structure of materials, and has played an important role in the study of iron-based high-temperature superconductors. The revealing and discovery of the Fermi surface topology, superconducting energy gap and its symmetry, three-dimensionality, orbital selectivity, and electronic coupling mode in different iron-based superconductor systems provide an important basis for identifying and proposing new theory of iron-based superconductivity to solve high temperature superconductivity mechanism.