Question: Is Objectivism a division of individualism, or is individualism a division of Objectivism? (philisophically speaking)
Answer: "Individualism" is a term for classifying theories, such as ethical or social theories. Any theory that places the individual foremost or in a fundamental position is a kind of individualism.
Objectivism holds that all knowledge comes, ultimately, through the rational interpretation of the evidence of the senses by an individual, for that individual. In ethics, it holds that each individual's life and happiness is the proper purpose of morality. In politics, it advocates individual rights to life, liberty, and property. So, certainly, Objectivism is a kind, or species, of individualism.
There are other types of individualism: Nietzsche's will-to-power philosophy is a kind of individualism, in a sense. A hedonistic, do-whatever-you-want philosophy would be a kind of individualism. Solipsism, cutting oneself off from the rest of society, is also, I suppose, a kind of individualism. None of these are compatible with Objectivism. So in this sense, Objectivism does not include all individualisms within it.
William R Thomas writes about and teaches Objectivist ideas. He is the editor of The Literary Art of Ayn Rand and of Ethics at Work, both published by The Atlas Society. He is also an economist, teaching occasionally at a variety of universities.