Valgrind is an open-source programming tool used for memory debugging, memory leak detection, and profiling applications. It helps developers identify issues in their code, such as improper memory usage, which can lead to crashes or unexpected behavior. By running a program under Valgrind, developers can analyze how memory is allocated and freed, making it easier to spot errors. The tool supports various programming languages, including C and C++, and provides detailed reports on memory usage. Valgrind is particularly useful for improving software quality and performance, ensuring that applications run efficiently and reliably in different environments.