A “monitor” traditionally described a speaker that’s intended for extremely accurate reproduction in a recording studio or other such professional setting, so that an audio engineer can effectively assess and adjust what they’re working on – to monitor the sound, so to speak. This is opposed to a regular speaker perhaps “coloring” the sound, so as to make it ultimately sound the best for the consumer.
As you can imagine, a true monitor speakers needs to be of very high quality, and they’re thus generally very expensive and not really marketed for residential consumers. Unfortunately, though, it’s become a trend for companies to kind of take advantage of these nice sounding descriptors, and many so called “monitor” speakers will have essentially the same specs and design as competing “regular” speakers. We suspect companies use the descriptor to make their product sound more professional and thus of ostensibly higher quality.
We recommend paying little attention to fancy sounding descriptors and simply focus on the important metrics: power handling, response range, crossover design, etc., as well as specs and features that are in line with what you’re looking for a speaker to do for you.