Using standard form is incredibly useful when we either need to use very large or very small numbers.
Other areas we may use standard form includes science. From measuring the distance between stars or the mass of atoms.
Remember
1000 = 103
100 = 102
10 = 101
1= 100
0.1 = 10-1
0.01 = 10-2
0.001 = 10-3
Examples
5.1 × 102 as an ordinary number is
5.1 × 100 = 510
3.214 × 10 -4 as an ordinary number is
3.214 x 0.0001 = 3.214 ÷ 1000 = 0.003214