A diaspora refers to a population that got exiled,enslaved,depossessed,etc because of war, famine, and etc. For an mass movement from one country to another be considered a diaspora. They must fulfill the following requirements:

1. Be expelled or lose large amounts of land, lives, or property.
2. Has a desire to influence affairs at home either to return or to assist in one shape or another.
3. Keeps at least a few cultural traits from the homeland but adopt new cultural features.
4. Considers themselves with a different identity than everybody else.

And there has been many examples of diasporas in the past and more recent ones thanks to wars and exoduses. Prominent examples in both recent times and past are:

The Circassians (mostly expelled from Russia in the 1800s; now live in the Middle East and parts of Russia)

Another example of a diaspora is the Jewish diaspora. Because after a series of exiles in the first to second century ce and various other pogroms and persecutions later on; the Jewish people later traveled all over the world. And many of them only came back in the early 20th century when Israel was declared as a country and the partition of Palestine.

The Tibetan Diaspora:

The Tibetan people currently still live in Tibet but a vast number of the cultural leaders and common people fled to India,Nepal, and the United States after Tibet was annexed by the Chinese military in 1959.

And there are many more diasporas all over the world like the Rohigyna, Palestinians,Mayan peoples,Chagossians,etc more than can be counted. Often, the discussion of diasporas and their relation to the country they are in now and attempts to return are quite controversial. But they need to be discussed since they are a important to deal with.

But we will focus on the biggest diaspora in the planet. The African Diaspora.