I cannot understand why the value of "palindrom" changes?

I cannot understand why the value of "palindrom" changes works when the condition

if(palindrome(i*j) ): 

is replaced with

if (palindrome(i*j) and i*j>palindrom)):

in this code

 def palindrome(n):
     return str(n)==str(n)[::-1];

 def ndigitPalindrome(n):
     lbound=10**(n-1);
     ubound=10**(n);
     palindrom=0;
     for i in range(lbound,ubound):
              for j in range(lbound,ubound):
                  if(palindrome(i*j) ): 
                      palindrom=i*j;
     return palindrom;

 print "Largest n digit palindrome : ",ndigitPalindrome(3);