A debugger in programming is a tool that allows developers to test, analyze, and troubleshoot code. It helps identify and fix bugs by providing features such as step-by-step execution, variable inspection, and memory management analysis. Debuggers enable the examination of the program's state during execution, making it easier to isolate issues and verify the logic of the code. Utilizing a debugger significantly improves software quality and reliability by ensuring that programs function as intended before deployment.