Function scope refers to the accessibility of variables defined within a function. When a variable is created inside a function, it is only available for use within that function. This means that other parts of the program cannot access or modify that variable, helping to prevent unintended interference and errors. In programming languages like JavaScript or Python, understanding function scope is crucial for writing clean and efficient code. It allows developers to create functions that operate independently, ensuring that each function has its own set of variables. This encapsulation promotes better organization and maintainability of the code.