Explain the Law of Multiple Proportions.

This law was proposed by Dalton in $1803$.
According to this law,if two elements can combine to form more than one compound,the masses of one element that combine with a fixed mass of the other element are in the ratio of small whole numbers.
For example,hydrogen combines with oxygen to form two compounds,namely,water $(H_2O)$ and hydrogen peroxide $(H_2O_2)$.
$1.$ Hydrogen $+$ Oxygen $\rightarrow$ Water $(H_2O)$
$2 \ g$ of Hydrogen combines with $16 \ g$ of Oxygen.
$2.$ Hydrogen $+$ Oxygen $\rightarrow$ Hydrogen Peroxide $(H_2O_2)$
$2 \ g$ of Hydrogen combines with $32 \ g$ of Oxygen.
Here,the masses of oxygen ($16 \ g$ and $32 \ g$) which combine with a fixed mass of hydrogen $(2 \ g)$ bear a simple ratio,i.e.,$16:32$ or $1:2$.