Performance bugs are issues in software that cause it to run slower than expected or consume excessive resources. These bugs can lead to delays in processing, increased loading times, or unresponsive applications, negatively impacting user experience. Common causes of performance bugs include inefficient algorithms, memory leaks, and excessive database queries. Identifying and fixing these bugs is crucial for maintaining optimal performance and ensuring that applications meet user demands effectively. Developers often use profiling tools to detect and resolve these issues, improving the overall efficiency of the software.