This video introduces C functions, starting with the familiar `main` function where program execution begins. The `printf` function, used to print to the console, serves as another example. Functions group functionality for reuse throughout a program, avoiding code repetition. The `printf` function, defined in a library, can be called multiple times to print different strings. Functions are a fundamental concept across programming languages, promoting modularity and code reusability. The video emphasizes their importance for organizing and structuring C programs, making them easier to understand and maintain.