An area with a much higher concentration of a particular ethnic or cultural group that doesnt dominate in the general population.
It could be as small as one side of a single block where all the residents are of Tibetan descent and the businesses are thusly themed...
or it could be as large as a 2 square mile area dominated by Spanish or Cantonese speaking population.
Also known as an enclave.
Visiting an ethnic neighborhood can be like entering an entirely different world. Save's a lot on travel expenses natch!