This is used for representing very large or very small numbers. A number in scientific notation is written as a decimal number between 1 and 10 multiplied by a power of 10, some examples:
International System of Units (SI) prefixes are names, based on powers of ten, and used to describe small or large quantities. For example, the prefix kilo means 103 = 1000; that is, a kilometer is equal to 1000 meters. Here is a table of SI prefixes:186,272 = 1.86272×105 0.0625 = 6.25×10-2
power prefix symbol name 1024 yotta Y Septillion 1021 zetta Z Sextillion 1018 exa E Quintillion 1015 peta P Quadrillion 1012 tera T Trillion 109 giga G Billion 106 mega M Million 103 kilo k Thousand 102 hecto h Hundred 101 deca da Ten 10-1 deci d Tenth 10-2 centi c Hundredth 10-3 milli m Thousandth 10-6 micro µ Millionth 10-9 nano n Billionth 10-12 pico p Trillionth 10-15 femto f Quadrillionth 10-18 atto a Quintillionth 10-21 zepto z Sextillionth 10-24 yocto y Septillionth