Amalek was the illegitimate son of Elifaz, and the grandson of Esav. (Amalek’s mother was the illegitimate daughter of Amalek’s father).
The progeny of Amalek are the archetypal enemy of the Jewish People. Their very existence is diametrically opposed to the Torah. The Sages describe the people of Amalek as being the essence of all the evil in the world.
Today, we don’t know who is descended from Amalek. Around the year 600 BCE, the Assyrian conqueror Sancheriv exiled most of the world’s inhabitants from their homelands and scattered them around the world. Since then, the true national identity of any people (except for the Jews) has become obscure.
The concept of "Amalek" goes a long way in helping us understand the baffling phenomenon of anti-Semitism. Anti-Semitism has no sociological parallel. Even the word is unique: "Anti-Semitism" is the only English word describing hate towards a distinct group of people. There’s no English word for French-hatred, Irish-hatred, or German hatred, even though England fought bitter wars against all these nations.
We are the only people in the world towards whom there exists a unique, distinct hatred. This bears out the Torah’s prediction that until the Mashiach’s days, there will exist a nation, Amalek, with an unexplainable, inborn hatred towards us.