[Sic] is Latin and means so or thus. It is used, always in brackets (not parentheses), immediately after an error in either speech or writing that is being quoted. It indicates that the writer who has used that quotation knows that the word immediately before [sic] is an error. It is used so that you, the reader, will know the error was not made by the writer you are reading but by the writer being quoted.
Incidentally, [sic] never indicates that any material has been omitted; to show that, you use ellipses (… at the beginning or in the middle of a sentence or …. at the end).