An Environment meter is a broad term that can refer to a multitude of devices. These devices measure a mixture of variables including temperature, humidity, airflow light and sound.
Instruments that measure one (and sometimes two) of these variables have their own names. Hygrometers (humidity), anemometers (airflow), sound and light meters (light/sound) and obviously thermometers (temperature).
Some devices are pre-fixed with the term 'thermo' such as a thermo-hygrometer. This simply means measures temperature.