The explosive charge is the main component of any bomb, and makes up most of the size and weight of it. It is the damaging element of the bomb (along with any fragments or shrapnel the deflagration might produce with its container or neighboring objects).
The detonator is the source of heat that will start the combustion (or chain reaction in case of nuclear explosives). It is itself an explosive, with a lower ignition point than the main explosive chargees.
List of notable incidents involving time bombs
On December 11, 1994, Philippine Airlines Flight 434, a Boeing 747-283B, was flying its second leg, from Cebu to Tokyo, when a time bomb exploded, killing one passenger. The rest of the passengers and the crew survived. The aircraft made an emergency landing at Naha Airport, Okinawa, 1 hour after the bomb exploded. The bomb was made of a Casiodigital watch as the timer and a bottle of liquid nitroglycerin as the explosive. It was planted under seat 26K by Al-Qaeda member Ramzi Yousef, who boarded the flight under the alias Armaldo Forlani. He planted the time bomb on the first leg from Manilla to Cebu, and left the plane at Cebu with 25 other passengers. The bomb exploded 4 hours after being planted. Yousef was arrested 2 months later in Pakistan.