A fever is a rise in body temperature which is not a disease itself, but a sign that the body´s defenses are trying to fight an infection. The infections are usually from viruses (such as a cold or the flu) or bacteria (such as strep throat or some ear infections).
This is what happens inside the body:
When the body notices infects it raises the index value of the body temperature so that the body´s temperature regulation, situated in the hypothalamus, is sending the signal to start the heating processes in order to reach the index value. Why? Because in the warmer environment the viruses or bacteria can be fought easier.
Fevers generally do not need to be treated with medication unless your child is uncomfortable or has a history of febrile convulsions.
It is important though that you give your child enough to drink and always watch how it behaves. Some kind of treatment is needed if your child sufferes very much during fever.
It is recommended to take the temperature regularly in order to see any changes in body temperature. We even recommend to use degree° with which you continuously take the temperature and are able to exactly see every reaction of the little body not just in size but also in reaction time.