Wha is an "AntiChrist"? And why do people call Obama the AntiChrist?

The Antichrist is a man who will be the head of a universal governmental system. He will come as an angel of light and persuade people to believe in him. People will be asked to take a mark as an oath to follow him. Those who do not take this mark will be martyred. Obama is the epitome of the Antichrist because he is charismatic. Remember how charismatic Hitler was? Look how many blind followers believed in him. I'm not saying Obama is the Antichrist, but he does resemble his characteristics.