what does rand do in C code example

Example: c rand

#import <stdlib.h>
#import <time.h>

int r;
srand(time(NULL));
r = rand();

/* 
This will give you a pseudo random integer between 0 and RAND_MAX. 
srand(time(NULL)) is used to give it a random starting seed, based on the
current time. rand() could be used without it, but would always return the
same sequence of numbers.
To generate a random number in between 0 (included) and X (excluded), do
the following:
*/

#import <stdlib.h>
#import <time.h>

int r;
srand(time(NULL));
r = rand() % X;