The origin of the term "Diaspora" is Greek and it comes from the verb "διασπείρω", which means "to scatter" or "spread about", and the word "διά" which means "across or through".
The aspect of Judaism that Diaspora is mostly directly linked to is the exile of the Jews from Israel. It's the dispersion of the Jews out of their homeland and their settlement in different countries and parts of the world.
Nowadays the term Diaspora is used to refer to any kind of population that is disseminated from their home land.
We could establish different types of Diasporas depending on each different cause of it. One example could be Imperialism (a nation extending its power by acquiring new land by military force or dimoplamy).
Effects from Diaspora could lead to or be linked to never fully integrating to the new nationor sometimes longing for the homeland, with mixed feelings of returning back.