The word diaspora refers to the scattering of people from their ancestral homeland. In the year 588 B.C., Nebuchadnezzar and the Babylonians overran the southern Jewish kingdom of Judah and destroyed the temple, precipitating an era of exile of the Jewish people. The period of the diaspora lasted around 2000 years, and Jewish diaspora communities were able to maintain a fair amount of autonomy in the lands they found themselves in.
There have been many other incidents of diaspora throughout history. Often, it is oppression that forces a population to leave their beloved homeland. It is reported that, since the invasion of Iraq by the United States, over half of the million Christians there have fled the country, creating a Middle Eastern Christian diaspora.
My most direct experience with the ongoing diaspora is connected to my association with Philippine Islands. The Philippines are wracked by poverty and held victim by corruption. Filipino workers scatter to the Middle East, to richer Asian countries, to North America – fathers leave their families, mother leave their children, children leave their parents -- all in a sacrificial movement to support their families, children and parents back home. It is safe to say that the livelihood of the Philippines rests on its diaspora communities. A related phenomenon in the Philippines, as it is in other impoverished countries, is the “brain drain” – i.e., people such as doctors, professors, engineers – leaving their homeland and depleting a level of professionalism on which a society relies. (This happens on a more localized level in the East Bay area of California, where I live. There has been a history of AfroAmericans isolated in ghettoes, primarily in Oakland and Richmond. As housing has become more accessible due to the housing crisis, some are moving into the suburbs, particularly in East Contra Costa. This is particularly the case in the more "upwardly mobile" residents, further depeleting the talent and skill in the communities from which they are moving.)
Countries today have recently experienced, and continue to experience, the influx of cultures due to an economic diaspora. The other side of diaspora is immigration. When the diaspora community finds itself in a new environment, members find each other and form their own community to surround themselves with the familiar and to retain some of its cultural heritage. Just as the autonomous Jewish diaspora communities, referred above, eventually impacted the communities where they settled, so modern “diaspora communities” touch the worlds where they are settled. (We can find a Mexican piñata at most North American children parties. My neighbors of every race and culture eagerly await the pansit and lumpia my Filipina wife prepares whenever she lavishes family and friends at holiday meals. Likewise we get our share of tamales!)