MemTest is a diagnostic tool designed to check the memory (RAM) of a computer for errors. It runs a series of tests to identify any issues that may cause system instability, crashes, or data corruption. By thoroughly examining the memory, MemTest helps users ensure their computer operates reliably. The tool is typically run from a bootable USB drive or CD, allowing it to test the memory outside of the operating system. Users can choose different test options and durations, making it flexible for various needs. Regular use of MemTest can help maintain optimal system performance.