Document 5 shows what apartheid was through Nelson Mandela's speech talking about how, "Africans want to be a part of the general population, and not confined to living in their own ghettos." And other things that happened under apartheid.
Document 5 also compares to another injustice happening today, in North Korea people are brainwashed to live the ruler, and the people are the weaker race, as where the governmental people are the stronger race, just like in apartheid. The weaker race didn't have the rights of the governmental people.
Apartheid was when the Africans were "weaker" then the whites / Europeans. This is just like something that happened in America. In America, African Americans were treated lesser than white people. The African Americans had way less rights then the whites.
It is so important to know what apartheid was so that history never repeats itself. If we forget about apartheid, then people forget the horrible fights, and the outcome, so it could one day repeat.