Normal should be defined by measuring a large number of people in a very accurate way. Different people probably also have a personal normal that is slightly different from the accepted number. Significance of elevation isn't clear. A very high fever, over 105 or 106 F is dangerous, but lower fevers probably cause no permanent damage. A fever is probably a temperature that is more than a degree or so above normal.
Various experts suggest different thresholds for calling an elevated temperature a fever.
Measurement of temperature should be done accurately. This can be done by inserting a thermometer probe through the rectum, down the esophagus, or into a large central blood vessel. On the other hand, these measurements are more easily and pleasantly accessed. However, there are large marketing efforts to sell these thermometers for home use. VrDr isn't too thrilled with using new technology that isn't a proven improvement.