What is the difference between nationalism and federalism? Thanks!

Answer 1

Every country may be ( and probably is) nationalistic. That is a feeling of pride in one's country.
http://plato.stanford.edu/entries/nationalism/
Not every country is federalistic.
That is a system of government.
http://plato.stanford.edu/entries/federalism/

Answer 2

Federalism is an idea where a central government shares power with lesser units. Keep in mind there are historical examples where nationalism has become unhealthy and led to wars.