In chemical reactions, what does the principle of conservation of mass mean?

I think It means that any balanced equation is conserved. Meaning that the equation is equal. The law states matter can’t be created or destroyed. In chemical reactions the mass of an element is the same before and after the product. There’s two sides two an equation the reactants side and the product’s side. Hope this helps.

Principle of Conservation of Mass
In simple terms, it means that in a chemical equation, the mass of the reactants is same as mass of products. No mass is created, and cannot be transformed.