If you are referring to PHP's rand function then.
The rand function is a function that is used to generate a random number between and including two fixed values or two varibles.
An example of this is:
<?php
$rand1 = rand(1,9);
echo ($rand1);
?>
This will generate a number between 1 and 9 including 1 and 9
Another exampe of this is:
<?php
$value1 = 1;
$value2 = 9;
$rand1 = rand($value1,$value2);
echo ($rand1);
?>
This is also generate a number between 1 and 9 including 1 and 9.
I hope this has helped you.