Patriotism is known as a pride for one's country. These are the kind of people that enjoy seeing their country succeed and generally support the country on whatever decision it makes (some decisions obviously anger patriots). Nationalism is the extreme form of patriotism and this is the one that causes civil wars. Nationalism is the belief that your country, or people (a peoples is also considered a nation), is superior to all other countries. Nationalists usually support country domination, sometimes in order to "save" similar cultures or people, or sometimes just to assert dominance.
Nationalism is also the term given to people who desire independence for their "society". An example of this would be the Confederate States of America. The Confederates disagreed with the government that was controlling them and desired to "save" their own people by declaring independence in order to fight a power that was considered a threat to their nation. Another example would be the nation of Afrika. This nation consists of nationalists who want to form a primarily African-American nation and declare their independence (don't ask why, I'm pretty sure this nationalist idea emerged from the Black Panther Party).