In programming, "null" or "void" refers to the absence of a value or an object. It indicates that a variable does not point to any data or that a function does not return a value. This concept helps developers manage memory and avoid errors when trying to access non-existent data. In many programming languages, such as Java and C++, null is a special marker. When a variable is set to null, it signifies that it is intentionally empty. Understanding null is crucial for debugging and ensuring that programs run smoothly without unexpected crashes or behavior.