Why do people believe in the anichrist?

most people from what i understand think theres gonna be this person called the antichrist that gonna be like the devils son or something but the bible says that is wrong here let us look up some scripture on the matter shall we? :1John 2:18" says there has come to be many antichrist while jesus was on the earth."1John 2:22" and "1John 4:3" and"2John verse 7"describes exactly what it means to be a anichrist.