What is the difference between 列车 and 火车 What is the difference between these two words? Both mean train. Is there any difference? Are they used in different regions?
Yes there are differences.

火车 literally means "fire car", and it got this name since the steam locomotive era when trains relied on buring coal as fuel. Later this word is generalized to refer to trains. But with modern technology developing, for example 高铁 (High Speed EMU Train), official media usually referes to it as 高铁列车, not 高铁火车. I guess it's because 火车 simply does not fit into the image. 电气列车, 地铁列车 and 轻轨列车 are some other examples.

However, the word 火车 is still used when referring to train in general. For example, 火车票 means "train ticket" and 火车站 means "railway station". You cannot replace 火车 with 列车 in these cases.

Technology aside, 列车 literally means "linked car(s)". So this word should also be used when the subject referred to is related to the linked cars (passenger units), not the locomotive (motor unit). Hence in the word 列车乘务员 (train conductor), you shouldn't use 火车, because the conductor serves the passenger units.