gdb, short for GNU Debugger, is a powerful tool used for debugging programs written in languages like C, C++, and Fortran. It allows developers to inspect the execution of their code, set breakpoints, and examine variables, helping them identify and fix errors in their programs. With gdb, users can run their programs step-by-step, which makes it easier to understand how the code behaves at runtime. It also supports features like backtraces, which show the call stack, and the ability to modify variables on the fly, enhancing the debugging process and improving code quality.