This app is a thermometer, which displays indoor and outdoor temperature (Celsius and Fahrenheit degree scale).

️ INDOOR thermometer:
Indoor temp. is taken from built-in phone temperature sensor (ambient temperature sensor). However, some devices are not equipped with this sensor and then the app uses the sensor of device's electronical subassembly (e.g. the phone battery). Unfortunately, such temperature can differ from the real ambient air temperature, so to obtain the most accurate one you should leave your phone untouched for an hour (the best way of getting the correct temp. is to check it just after waking up, after your phone hasn't been used for the whole night).
Moreover, to get more proper results, you can use calibration menu. How to do it? Check inside room temperature using real thermometer. Run calibration menu. Adjust inside temp. displayed by the app to fit value from thermometer.

️ OUTDOOR thermometer:
Outdoor temp. is taken from the weather web service. App needs access to your phone's location in order to determine your position. It sends your coordinates to online weather service. Service checks for nearest weather stations and provides actual outside temperature.

Why does the app need an access to device's location?
In order to check outside temperature app needs to know your current position.

Why does the app need an access to internet?
In order to check outdoor temperature in the nearest weather station, app needs to send request to online weather service.