Apparent (“feels like”) temperature. This number is an approximation of how the air temperature might feel to a human observer.
Above 26.7C, this is the heat index which combines the effect of temperature and humidity.
Below 10C, this is the wind chill factor which combines the effect of the temperature and wind chill.
At temperatures from 10C - 26.7C where neither of these is true, this value is just the air temperature.