Defect comprehension is the study of establishing a complete cognitive process for the defect itself and its derivatives. Because of the coherence of debugging and the incomprehensibility of information under the assumption of perfect bug understanding, through analysis of defect propagation process and the relationship between defects, research on key information detection and understanding information expression, extraction, and expression of understandable information for different scenarios and different needs of defect research, ultimately achieving the goal of optimizing defect analysis results and assisting the reuse and accumulation of defect knowledge in debugging process becomes inevitable. This study starts from the problem of knowledge fragmentation between location and repair, considers the essence of defect understanding research, clarifies the lack of knowledge mining and interoperability in the process of defect handling. Through the summary of engineering examples and the analysis of literature results, the research directions and technical methods in the field of defect comprehension are summarized, the characteristics and difficulties in the study of defect comprehension are discussed, the existing problems in the study and the future research directions are considered, and the research trend of defect comprehension is prospected.