The term "monitor" has several meanings, depending on its context.
In general usage, a monitor is an electronic device that displays visual information from a computer or other source. This could refer to a CRT (cathode ray tube) display, LCD (liquid crystal display), LED (light-emitting diode) screen, or any other type of screen used for displaying images and text on a computing system.
In the field of audio engineering, a monitor is an output signal that is sent to a set of loudspeakers so that performers can hear themselves while they are performing. This allows them to adjust their volume levels and balance within the ensemble without having to rely solely on the main mix coming from the soundboard.
In biology, "monitor" refers to certain species of lizards belonging to the family Varanidae, which includes the famous Komodo dragon. These large reptiles are native to tropical regions of Asia and Australia, and are known for their powerful bite and ability to take down prey much larger than themselves.
In a more general sense, "monitor" can also refer to someone or something that keeps watch over an area, system, or activity, in order to detect any unusual or unexpected events and respond accordingly. This could be applied to anything from security cameras monitoring a building or neighborhood, to software programs designed to monitor network traffic for signs of malicious activity.