technically speaking, that's like asking what the difference is between Lutherans and Christians, or Methodists and Christians.
Catholicism is a Christian religion, just like being a Baptist, Methodist, Presbyterian, Lutheran, or any number of other denominations is still being Christian.
Of course, there's also the SEARCH FUNCTION which would lead you to <a href="http://www.tfproject.org/tfp/showthread.php?s=&threadid=47874">this thread</a>
Please take any further discussion there.