With the increasing complexity of software systems, it becomes very difficult to install, configure, adjust, and maintain them. As systems become more interconnected and diverse, system architects are less able to predict and design the interaction between components, deferring the handling of these issues to runtime. One of the important problems that occur during execution is system failures, which increase the need for self-healing systems. The main purpose of self-healing is to have an automatic system that can heal itself without human intervention. This system has predefined actions and procedures that are suitable for recovering the system from different failure modes. In this study, different self-healing methods are categorized and a summary of them is presented.