Ghetto technically refers to a neighborhood into which a racial minority tends to be segregated. It comes from Jewish ghettos enforced legally in Europe in the 16th century, but it is also used for neighborhoods where minorities live for other reasons (such as social or economic pressure).

Project refers either to public housing, or more generally any group of buildings where economically disadvantaged people tend to be segregated.

Because these very frequently overlap in the US, people often use them interchangeably.