Most people are familiar with the term "segregation". Certainly, if you are from the Southeast United States, you are familiar with the term.
Segregation refers to forcibly separating people based on their race and/or ethnicity.
The state of Alabama is infamous for its efforts in the 1960's to maintain segregated schools.
However, other terms related to this concept may be a little less familiar.
De jure segregation relates to racial separation forced by specific laws. All such laws were eliminated in the U.S. by the mid-1960s. Because these laws were eliminated in the 1960's, de jure segregation is a concept that no longer exists . . . technically . . .
DeFacto segregation relates to "matter of fact" separation. Specifically, this type of segregation exists in terms of neighborhoods and school districts. It is not legally mandated for African-Americans and Caucasians to live in certain areas, but it is a fact that this phenomenon occurs.
I found these definitions at an interesting website . . . The New Dictionary of Cultural Literacy