Something that's pyrotechnic has to do with fireworks. Many Americans watch pyrotechnic displays on the Fourth of July.
You can use the adjective pyrotechnic to talk about fireworks, including making them or watching them. You can also use it to describe things that look like fireworks, like pyrotechnic sparkles of sunlight through a prism, or pyrotechnic sparks in your backyard fire pit as you throw pine branches on the blaze. Pyrotechnic first meant "of fire," from the Greek pyro, "fire," and tekhnikos, "made by art."