Chain migration is where one group of a certain culture attracts more people of the same culture/lifestyle/viewpoint to come to the country as well. Economic factors may play a role but it's not the definitive rule. For example, Chinatown in San Francisco is a small enclave where Chinese immigrants set up home, shops, etc which in turn brought more Chinese to join the small "city" within a city. Other examples include
- Little Italy in New York
- Little Havana in Miami Florida (Havana is a city in Cuba)
- Little Mogadishu in Minneapolis, Minnesota (Mogadishu is a city in Somalia, Africa)
- Various other Chinatowns throughout the US (eg: one is found in Houston, another is found in New York).
These are known as ethnic enclaves.
There are tons more examples out there so feel free to do more research. Each enclave is fairly homogeneous meaning that there is one main culture in that small city within a city. As more of these mini cities form, we have more of a melting pot going on. Look at any very large city such as New York and you'll see various mini cities that interact with one another in some way. These mini cities allow people to retain their customs, language, etc but in some aspects they must adopt ideas from the main location in which they are located. For example, immigrants are expected to learn English in the United States, but of course there are options such as translations.