Detonators are components of explosive system, containing a primary explosive but also a housing for the initiating explosive and the pyrotechnic or electrical parts needed to initiate the primary explosion. Among the simplest detonators is the electrical or nonelectrical (i.e., triggered with a burning fuse) blasting cap for manually placed explosives, under reasonable environmental conditions.
Detonators in weapons are much more of an engineering challenge, if only that they variously may have to withstand the immense acceleration of being fired from a gun, heat and vibration in flight, and such things as impacting on the target. There is no precise line between a fuze, which, for example, might sense impact and penetration, and a detonator; the detonator is arguably a component of a fuze.
Some of the most demanding applications for detonators are in the implosion systems of fission devices, where they must be extremely fast, high in explosive energy, and able to be synchronized with other detonators. The slapper detonator was a second-generation detonator for this application, now used in non-nuclear weapons.