They use gasoline or some similar substance that does burn very brightly. When they are refering to is explosions from bombs and grenades and suck which essentially just emit a “bang” and a cloud of dust and debris.
I think the “ring” effect seen in Star Trek and Star Wars and other movies is a bastardization of several real world phenomenon:
A large explosion in space would emit debris in a roughly uniformly expanding sphere of debris. As the sphere continues to expand, it would appear thicker around the edges and would thus appear as an outwardly expanding ring to an observer.
Gravitational forces around a large rotating mass would eventually pull the debris cloud into a Saturn-esque ring.
In the atmosphere, a large explosion emits a visible shockwave as it kicks up dust on the ground and the pressure change cause a change in the refraction index of the air.
So special effects folks have turned that into “large explosions create a ring”.
“Nuclear weapons have been tested by dropping them from planes (an “airdrop”), from the tops of towers, hoisted from balloons, on barges at sea, attached to the bottom of ships, and even shot into outer space by rockets (for the latter see below)… In 1963, all nuclear and many non-nuclear states signed the Limited Test Ban Treaty, pledging to refrain from testing nuclear weapons in the atmosphere, underwater, or in outer space…The Thor Missile was also used to loft warheads into near-space to conduct tests; these shots were collectively called Operation Fishbowl.” More to follow.
The High Altitude Nuclear Test Program was a study to determine the effect of a nuclear detonation in space on satellites and space itself. In project Argus, three rockets carrying nuclear weapons were detonated in 1958 to study the behavior of free electrons in the earth’s magnetic field. The military was also interested in the effect these explosions would have on the Explorer IV satellite, which would be used to monitor the tests. Argus showed that "A nuclear explosion in space produces three kinds of effects of military importance. The high energy radiation including particles from the explosion produces effects on space; the whirling high energy electrons generate radio noise; and the delayed radiation from the fission products can affect radio transmission [1]. It was observed later that the electrons striking the metal surfaces of satellites produce bursts of X-rays, which can damage electronics.
A later project (Fishbowl) which detonated a 1.4 megaton yield warhead at an altitude of 248 miles caused considerable havoc with Pacific communications, power systems in Hawaii, and damaged three satellites in orbit. The military decided that this adverse effect on friendly hardware would be an inevitable result of the use of high-yield nuclear warheads in space.
You put a cannister of gasoline or some other volatile on top of a modest amount of high velocity explosive, like a high-grade dynamite or a nitroaromatic compound; the explosion first aerosolizes the gasoline and then ignites it, producing the big, orange-red angry cloud so familiar to movie-goers. Dynamite or demolition explosives by themselves just produce a kind of flat bark with little or no flame, and extremely high brisance explosive compounds like those used in military weapons can produce a visible wavefront of compressed air followed by a sharp bang.
One can, as previously mentioned, make shaped charges that will produce asymmetrical explosions, but in general, when you blow something up the explosion is radially symmetric. (Nuclear ground burst and other very large explosions flatten out due to air pressure and earth boundary.)