The `stuff` function in SQL is a string manipulation function that replaces a specified number of characters within a string with another string. It's particularly useful for tasks like cleaning up data, inserting values into specific positions, or modifying existing text. Understanding how to use `stuff` effectively can significantly improve your ability to work with text-based data in SQL databases. It's important to note that the `stuff` function operates on character data types, such as VARCHAR, CHAR, or TEXT. It's not designed for numerical data manipulation. The function takes several arguments, making it flexible for various string modification needs. A common use case is to remove or replace specific substrings within a larger string, which is crucial for data cleaning and transformation.