Tactical flashlights is a relatively new descriptive term. It came about when high-performance LEDs and corresponding micro-circuitry were developed to the point of making super-bright flashlights very small and viable for consumer use. Actually, super bright is an understatement: a tactical LED flashlight can put out enough light energy to temporarily blind an attacker's dark-adapted eyesight. Some are so bright that they cannot even be looked at by people who have been out in the noonday sun.
The most practical rating of a light's output is rated in lumens. Do not be misled by candlepower claims from any tactical flashlight manufacturer; the higher the lumens, the brighter the light output. LEDs can also vary greatly in quality and color temperature. Color temperature is not about heat but rather the color of the light output. The ideal is a bright white light to illuminate the night, and some LEDs have an unpleasant bluish tint to their light.
Be aware that there are some color LED lights that can be considered tactical for special purposes. A red or green LED is preferred by hunters who do not want to spook animal prey. Animals have a difficult time discerning the red and green light output whereas a white light would startle them. A green, high-output, LED flashlight is extremely painful and blinding to human eyes.
The bulk of the cost of a tactical flashlight is in the LED and the controlling circuitry. Tactical flashlights use lithium CR123 batteries that can catastrophically fail if the light is not well engineered and manufactured. There have been reports of lights exploding or overheating to the point of catching nearby objects on fire. It's good to only buy from a manufacturer who has a proven track record. Remember, you get what you pay for.
Many may wonder why one 200-lumen light costs a fraction of another manufacturer's model of the same output, and the answer becomes evident when the individual components are closely examined side by side. LEDs are sold to manufacturers in bin lots. One bin of a type may vary in quality from another bin of the same type. Manufacturers know this, but the information is lost to many consumers. This reiterates why it is important to only buy from a trusted manufacturer. In other words, if you want the best quality, use the same lights that soldiers and special law enforcement teams use.