The acoustics of the room you are working at affects the sound you hear from the monitors. This is a major problem in recording and mixing. Certain frequencies will tend to resonate depending on the size and type of the room. This has something to do with the air in the room that causes vibration.
Naturally, to cure this perceived imbalance of frequencies, an engineer would apply an EQ correction. But since this is correcting a problem that only exists in the room, and not in the recording, then the recording will actually have a dip at these frequencies. Hence, it’s not good.
Read more about this here: https://www.audiomasterclass.com/newsletter/can-a-plug-in-improve-your-monitoring-acoustics