Who is Jack??

"Jack Bauer is the main protagonist in the American television series 24. Bauer trained and worked in various capacities as a government agent, including US Army Delta Force, LAPD, SWAT, and finally the Counter Terrorist Unit (CTU) Los Angeles. He is a key member of the latter and has prevented major terrorist attacks on the United States, saving both civilians and government leaders. He has done so at great personal expense, as those he has thwarted have targeted him and his loved ones many times."

Taken from: http://en.wikipedia.org/wiki/Jack_Bauer