What is the string handling functions present in header file <string.h>?

There are number of string handling functions present in string.h. In other words if a programmer uses any of the function present in string.h then they must include the header file as

#include <string.h> 

Some of the functions present in <string.h> are given below:

strcat() – This function is used to con concatenate two strings.
strcmp() – This function is used to compare two strings.
strcpy() – This function h is used to copy the second string given as second parameter to this function into first string.
strlen() – This function is used to length of the string in other words the number of characters present in string .
strstr() – This function is to obtain the first occurrence of substring in a string .