data is the result you get by making a measurement. If you use a tape measure to find the height of your two sister, the data would be 5 feet, 6 inches and 4 feet 9 inches. If you use a thermometer to find the temperature outside and inside, the data would be 95 degrees F and 78 degrees F. The result of a single measurement is a datum, data is plural.
Data... data is raw. It simply exists and has no significance beyond its existence (in and of itself). It can exist in any form, usable or not. It does not have meaning of itself. In computer parlance, a spreadsheet generally starts out by holding data.