Who are the Shi'ah, what are their sects, and do we declare any of the sects disbelievers?

The questioner : May Allah reward you with the best reward, O honorable Shaykh. By the grace of Allah, I teach a geography course at the university. One of the students asked me, when I was dividing the world's population by religion, that there are islands in the African continent called the Comoros, and that the Shi'ah have spread there. He asked me: Who are the Shi'ah? What are their sects? And do we declare any of these sects disbelievers? So I postponed the question until I could ask you.

The Shaykh : Yes, this answer requires elaboration. Look at the monitor. Let's have one question.

The questioner : A brief answer, may Allah reward you with good.

The Shaykh : Now, a brief answer will not do, because this matter is serious. Yes.