A kilogram is a unit of measurement that's a bit more than two pounds. The liter bottle of soda in your refrigerator weighed about one kilogram when it was full.
The United States is one of only three countries that has not adopted the metric system as its official system of measurement. In the United States, then, the pound is the basic unit used to measure mass, while most countries use the kilogram. So your bulldog weighs in at 100 pounds at your home in Florida but 45.36 kilograms when you move to Ireland. Originally, a kilogram was defined as the mass of a liter of water.