This law is related to the net enthalpy of the reaction. In Hess Law's reaction, each step should be balanced and reaction conditions should be constant for all the steps in the reaction.
The Hess law equation will be
The enthalpy change in a reaction represents the heat absorbed or heat released during the reaction. The negative value of indicate that heat is absorbed while the positive value indicates heat is released. When all the enthalpy changes are added, we get enthalpy change in each step of the reaction. While the difference between final and beginning enthalpy, we get net enthalpy change.