Definition (taken from Wikipedia) Yellowface is a form of theatrical makeup used by non-Asian performers to represent an East Asian person. It is similar to the practice of blackface used to represent black performers. Yellowface has been historically prevalent throughout Hollywood films, and continues to be used in the present day. Many writers have noted that portrayals of East Asians in the American film industry generally reflect an ethnocentric perception of them rather than realistic and authentic depictions of Asian cultures, customs, and behaviors.
This is a practice that is neither ancient history or buried in the past. Nor is it isolated to cultural backwaters; it is often done on in major metropolitan areas like New York, San Diego and Seattle. It helps to know some of the VERY recent history of brown and yellowface in theatre.