Scientific notation

Scientific notation is expressed as a power (also called an exponent) to the base 10. The superscript (called the exponent) represents essentially how many zeros there are in an measurable amount. 

A diagram showing the parts of scientific notation of numbers.

If the exponent is a negative value like -3 it means the value is very small ( getting close to zero). If the exponent is positive it is a very large value getting closer to infinity

Any numbers in front of the 10 are called significant digits.

For example 6.0221415 x 1023 (Avogadro's number) is a very large number. On a calculator there is a special function for the that '10' bit. often it is written as e or EXP

so 6.02x1023 can be written as 6.02e23 ( because a superscript is sometimes hard to show in plain text on calculators)

10-4 =0.001

10-3 = 0.01

10-2 = 0.1

10-1 =1

101 = 10

102 = 100

103 = 1,000

104 =10,000

105 = 100,000

106 = 1,000,000 (1 million)

107 = 10,000,000 (10 million)

108 = 100,000,000 (100 million)

109 = 1000,000,000 (1000 million aka a billion or milliard)

An example with atoms

So, if atoms are 99.9999999999999% empty space. This means atoms consist of 10-12 of something, eg nucleus and a cloud of electrons. ( the electrons are not often considered)

But if you take 10-12 and multiple this by 1023 (just add the exponents), you get 1011 of actual stuff, which is quite a lot. 

1 mole of carbon weighs 12.0096grams and has actually 6.0221415 x 1023 atoms in it. 

1 mole of water (H2O) weighs about 18grams and that also has 6.0221415 x 1023 atoms too.

Since you have a lot of water and carbon in your body there are well over 1011 bits of stuff interacting with you and surroundings. Say you are sitting on plastic chair, that has lots of carbon too. There are almost the same number of atoms interacting (though tiny electrostatic interactions) at the same time while sitting on a chair.