The function strdup is a standard library function in the C programming language used to duplicate a string. It allocates memory for a new string and copies the content of the original string into this newly allocated space. The function returns a pointer to the duplicated string, which can be used independently of the original. When using strdup, it is important to remember to free the allocated memory using free when it is no longer needed to avoid memory leaks. The function is defined in the header file string.h and is commonly used in various applications that require string manipulation.