I am assuming $row was created from something like
$row = mysql_fetch_array($result);
where $result is the output result set from a database query.
If so, then say each row of data in $result contains 3 columns of data - firstName, lastName, emailAddress.
$row will refer to the first column's data - firstName
$row will refer to the secon column's data - lastName
and so on.
Instead of using an indexed array you could use mysql_fetch_assoc() instead which returns an associative array for $row. In this case you can refer to the column names by their actual returned names in $result.
So the value for firstName in a row could be referenced with $row['firstName']