Surroundings in the Thermodynamic system: Everything around a system is called surroundings. Air on all sides of the cylinder with a piston is an example of this. In another way, any system with which an exacting system can exchange energy is called the surroundings of that exacting system. Whatever thing those are outside from the system will be termed as surrounding and system will be divided by the surrounding with the help of a boundary which is termed as system boundary.
In a thermodynamic analysis, the system is the matter of the investigation. A boundary is a closed surface surrounding a system through which energy and mass might come in or depart the system. Everything external to the system is the surroundings. A system can exchange energy with its surroundings by doing work or by the flow of heat.