While the original usage of "pyrotechnics" referred to fireworks, there are a wide range of engineering applications for pyrotechnic components, which use small quantities of explosives to achieve a desired mechanical result.
For a number of applications where a bolt or other fastener absolutely must release, at a precise time, and without human hands, pyrotechnic bolts and other fasteners are ideal. The explosive, when triggered, cuts the fastener.
Pyrotechnics can generate large volumes of gas, or, when appropriate, clouds of finely divided particles. A very common application is the gas generator used to inflate an automotive air bag, which commonly uses a desensitized version of the explosive lead azide.
Explosive forming and welding
The ancestors of explosively formed projectiles variously etched patterns into hard objects, or welded them together.