This paper reviews the literature related to the learning and teaching of debugging computer programs. Debugging is an important skill that continues to be both difficult for novice programmers to learn and challenging for computer science educators to teach. These challenges persist despite a wealth of important research on the subject dating back as far as the mid 1970s. Although the tools and languages novices use for writing programs today are notably different from those employed decades earlier, the basic problem-solving and pragmatic skills necessary to debug them effectively are largely similar. Hence, an understanding of the previous work on debugging can offer computer science educators insights into how to improve contemporary learning and teaching of debugging and may suggest directions for future research into this important area. This overview of the debugging literature is organized around four questions relevant to computer science educators and education researchers: What causes bugs to occur? What types of bugs occur? What is the debugging process? How can we improve the learning and teaching of debugging? We conclude with suggestions on using the existing literature both to facilitate pedagogical improvements to debugging education and to offer guidance for future research.