A RAM Tester is a diagnostic tool used to check the functionality and performance of a computer's Random Access Memory (RAM). It helps identify issues such as faulty memory modules, which can lead to system crashes, data corruption, or slow performance. By running various tests, a RAM Tester can determine if the memory is operating correctly or if it needs to be replaced. These tools can be software-based or hardware-based. Software RAM Testers, like MemTest86, run tests during the computer's boot process, while hardware testers are standalone devices that directly assess the memory modules. Using a RAM Tester is essential for maintaining system reliability and performance.