Summary

A function is a reusable block of code that performs a task. It has a function_name, optional function_parameters, and a body. You call it with arguments and it may produce a return_value. Functions support code_reuse, abstraction, and modularity. The function_signature describes its name and parameters. If no return is given, many languages provide a default like void_or_none. A function can read input_values, use local_scope, and may cause side_effects such as I/O.