To Jewish people. What is the difference between a Rabbi and a high priest(Cohen)?

A rabbi is not a priest, neither in the Jewish sense of the term nor in the Christian sense of the term. In the Christian sense of the term, a priest is a person with special authority to perform certain sacred rituals. A rabbi, on the other hand, has no more authority to perform rituals than any other adult male member of the Jewish community. In the Jewish sense of the term, a priest (kohein) is a descendant of Aaron, charged with performing various rites in the Temple in connection with religious rituals and sacrifices. Although a kohein can be a rabbi, a rabbi is not required to be a kohein.