Flamethrowers launch a flammable liquid and can light that liquid. They have a longer range and the fuel they project generally sticks and continues burning after hitting a target. Propane torches just burn propane at their nozzle their range is much shorter and don't really pose a danger outside of a few feet. This [0] is a flamethrower and this is a propane torch [1].

The Tesla Flamethrower is literally just a roofing torch like in [1] with a plastic gun around it and the valve turned all the way open. [2]

[0] https://upload.wikimedia.org/wikipedia/commons/transcoded/3/...

[1] https://www.youtube.com/watch?v=UprliuSNvX0

[2] https://qz.com/1191685/elon-musks-boring-company-flamethrowe...

Depending on the worth of pictures I might save some words here.

Weeney propane torch: http://gigadgetstech.com/wp-content/uploads/2016/11/Organic_...

A real flamethrower: https://flamethrowerplans.com/wp-content/uploads/2016/03/Fla...

Or, as others have already described, one burns a flammable gas and puts out a flame a few inches long. The other squirts flammable liquid at you from a long ways away, then ignites it. </vast_oversimplification>

A torch is essentially ignited butane (like a fancy lighter or Bunsen burner). A flamethrower is ignighted gasoline (or napalm). A flamethrower's flames stick and have a much further range.

A flamethrower is essentially a gasoline/napalm hose / stream with a lighter at the end of it.

Flamethrowers 'launch' a flame a long distance, typically by igniting some liquid and spraying it over a distance. A torch generally creates a much more localized flame. It's a much more controlled device.