Thermometers are devices used to measure temperature of the target. Typically, they fit into a palm. During the COVID pandemic thermometers have become indispensable when measuring the human temperature.
There are many types of contact and contact-free thermometers to choose from.
There are digital thermometers, which measure the temperature with a heat sensor. They can be used to measure the temperature in your mouth, rectum or armpit, but they need to be in physical contact with your skin to measure accurately.
Digital ear thermometers measure the temperature inside the ear through infrared ray technology.
Forehead (or temporal) thermometers resemble gun and are contact-free. They use infrared sensors to measure the temperature. The temperature is usually measured on the forehead and they have become very popular for use in airports, stores, stadiums and other public places.
There are also other types such as mercury thermometers. Their use has, however, declined, due to the dangerous aspect of mercury which becomes highly toxic and poisonous if the thermometer gets broken.