Memory usage refers to the amount of computer memory that is being utilized by programs and processes at any given time. This includes both the RAM (Random Access Memory) used for active tasks and the storage space occupied by files and applications. Efficient memory usage is crucial for maintaining system performance, as excessive memory consumption can lead to slowdowns or crashes. Monitoring memory usage helps users and system administrators identify which applications are consuming the most resources. Tools like Task Manager on Windows or Activity Monitor on macOS provide insights into memory allocation, allowing for better management of system resources and optimization of overall performance.