Your body's temperature is a balance between heat production and heat loss. This balance is controlled by the hypothalamus in your brain, which acts as your body's thermostat to maintain a set body temperature.
Fever occurs when the body's thermostat is reset to a higher degree.
Since each individual is unique there is no one specific number for normal or abnormal. To check your temperature you need a thermometer. There are many different kinds of thermometers with a wide range in price and convenience. That's because chills result from the need for muscle activity to raise heat production and increase body temperature. Most fevers resolve within 48 hours.