The article discusses how regression analysis can be used to understand and predict the frequency of events like doctor visits or car accidents. The authors provide a comprehensive guide on different models and methods for analyzing this type of data, making it easier for researchers and practitioners in various fields to use these techniques. The new edition includes updates on theoretical topics, cross-section models, inference methods, time series analysis, and more. The key findings highlight the importance of regression analysis in interpreting count data and the practical applications across different disciplines.