The prefix kilo- means what?

kilo- means 1,000.

kilogram = 1,000 grams
kilometer = 1,000 meters

http://www.thefreedictionary.com/kilo-

The prefix kilo- is a metric prefix that indicates a factor of 1,000. It is derived from the Greek word "khilioi," meaning "thousand." When used in measurements, it represents a multiplication by 1,000. For example, a kilometer is 1,000 meters, a kilogram is 1,000 grams, and a kilobyte is 1,000 bytes.