How does the principle of conservation of mass relate to chemical reactions? what information does a chemical equation give you?

The principle of   conservation  of mass relate  to chemical   reactions as below;

According to the principle of mass conservation atoms  are  not created  or  destroyed. They just  rearranged.Therefore  the   total mass of the product is  equal to the  total  mass of the product  since they contain  all  the same bonded together  in different  order.

The     information  that  chemical equation  give  is

 When equation is balanced  it give   information  about;   which substance  is  a  product  and which is a reactant.I how  much  Of each substance  is  involved. the relationship to each other.It also give  the steps that occur  during  the reaction.