Cloning is when a genetic copy of a living being is created. It is usually done by breeding the clone from birth, but there are methods to accelerate the process.
It is illegal to make a clone of a human, but it is sometimes done by the richest and most powerful people, especially on Earth. It is usually covered up by slightly altering the DNA of the clone. Giving the clone a different hair color, build, or gender.
Clones are genetic duplicates, but their minds are still free. It is considered culturally heinous to try to manipulate a clones mind, and the only place it happens on a semi-regular basis is on the Dark of the Moon.