This is a very hateful term used by racists to demean people from Africa or people of African decent. This word was used in the southern part of the United States during and after slavery to make black Americans feel like they were less worthy than white Americans.
Some people still use the term today if they are trying to insult a black person. This word is considered hate speech in the United States and if it is used in an official capacity, the person using the word could be prosecuted in a court of law in the United States. It is not an acceptable term to use in any way.