A kilometer is equal to 1,000 meters or 0.62137 miles. This is the primary measure of large distances throughout most of the world, though the United States still uses the mile as its standard.
Officially, the definition of a meter is the length of the path travelled by light in a vacuum during a time interval of 1/299,792,458 of a second. Therefore, the official definition of a kilometer is ten times that distance, which happens to be 1,000 meters. For a real world comparison, imagine Central Park in New York City. It is 849 meters wide — just short of a kilometer — and approximately 4 kilometers long.