A kilometer is a metric unit of measurement that is used to measure distance. One kilometer is 1,000 meters. It is equal to .62 miles.
The metric system was designed to be universal, and the United States is the only industrialized country that has not adopted it as its official system of measurement. In the United States, metric units are widely used in science, military and industry, but are generally not used by the public.
The metric system uses coherent base units of measurement with powers of 10. The metric system has changed and developed since it was first introduced, but the general concept has changed very little.