Answer:
It is important because it separates the area that the process is happening from its surroundings, and it's easy to measure and make observations by doing that.
Explanation:
The system is the part of the universe that is separated for study. It has a frontier, which is the limitation of it, and the external area is the surroundings.
In the system the chemical and physical process is happening: reactions are taking place, gas is expanding, heat is being absorbed or lost, etc.
So, to understand the process that is happening, it's necessary to define the system under study because the measurements, analyze, and observation will be easily done.
