A flare is a signal device that produces a bright, colored flame and smoke that is visible for miles from a good location.
Flares were first used as signal devices aboard ships, such as when a ship is in distress, which is the most common use for rocket and projectile flares. There have always been military applications as well, currently flares are used as decoys for heat seeking missiles on many aircraft. Formerly, before night vision devices/night vision goggles (NVD/NVG) were common flares were used to light the night sky so the enemy could be seen moving out of their positions (i.e. attacking).
Unfortunately flares tend to be bulky, heavy, and their flame has a relatively short lifespan so they should generally be used to compliment simpler permanent signal devices such as signal mirrors. On the plus side they can be used to start a fire in a hurry, even with wet material. In some cases flares can also be used for lighting, though this is limited in it's application as a lighting device as flares, even attached to a parachute, are of short duration.
- Road or Safety Flares - Sulfur based 30+ minute flare typically used to mark road hazards, also good to start fires with
- Rocket Flare - Single shot self-contained signal flare of various types (red star, parachute, etc.)
- Flare projectile - Flare guns (e.g. Very pistol) or conventional firearms fire flare projectiles of various calibers: 12 gauge, 1" or 25mm, 26mm or 4 gauge.
Note that it is both unsafe and illegal to convert any flare gun to fire any projectile (conventional or unconventional) ammunition.