At its core, multiculturalism is the idea that people of different cultures can co-exist peacefully and in close proximity; it favors the idea of preserving different cultures or cultural identities within a unified society, rather than requiring immigrants to discard their native customs and adopt local ones.
Underlying this core is the idea that other cultures are nifty and interesting, rather than being a threat of some sort; this is in opposition to ideas such as nationalism ("my country is the best country, and people from other countries are therefore inferior"), certain forms of patriotism ("my country must be defended even when it does bad things") and, in a sense, evangelism ("my culture's ideas are indisputably so much better than your culture's ideas that I need to convince you to adopt my ideas without listening to yours").
Multiculturalism is a significant feature of liberal ideology.
The phrase "cultural diversity" generally refers to the goal of multiculturalism, i.e. that of preserving individual cultures within a society, regardless of their origin.
 Mixed Success
While some countries such as the United States have enjoyed great success (at various times and places) with this idea, it has been much more of a problem in other parts of the world. The reasons for this discrepancy remain unclear, but one cause (e.g. in Europe) seems to be political /distortion of the term's meaning.
 Differing cultural responses
Cultures that value harmony (even if largely in an outward way) seem less likely to respond to perceived immigration in an angry and organized way.
Over time immigrants from different waves of immigration tend to become accepted and considered as part of society (assuming there is no civil war or other serious conflict) even to the extent that they will share in negative attitudes towards later waves of immigrants.
- Why have some societies rejected multiculturalism, and is this a valid response?