What are UDFs (User Defined Functions)?

UDFs, or User Defined Functions, are custom functions created by users to perform specific operations that are not available through built-in functions in programming languages or data processing tools. They are commonly used in databases, spreadsheets, and big data frameworks like Apache Spark or SQL to extend the capabilities of standard functions. UDFs allow for more flexibility and customization when working with data, enabling users to define their own logic for processing or analyzing data. However, they should be used judiciously, as they can sometimes impact performance compared to built-in functions.