Software maintenance refers to the process of making modifications or updates to a software system after it has been deployed. This can include fixing bugs, adding new features, improving performance, enhancing security, and updating documentation. Software maintenance is a critical aspect of the software development lifecycle, as it ensures that the software continues to meet the needs of its users and remains functional over time. Maintenance activities can be classified into corrective maintenance (fixing bugs), adaptive maintenance (making changes due to external factors like operating system upgrades), perfective maintenance (improving performance or adding new features), and preventive maintenance (proactively optimizing the software to prevent future issues). Overall, software maintenance is essential for ensuring the longevity and effectiveness of software systems.