What are surroundings in the thermodynamic sense?
Answer: The mass or region outside the system is called the surroundings.
or "everything else outside the system boundary" is surroundings.
Examples:
For a condenser in the domestic refrigeration system, the room is the surroundings
For the radiator of a car, the outside (Earth) is a surrounding
If a house is taken as a system under study then the town is the surroundings and if the entire town is taken as a system then the country is the surroundings.
What is a system?
A system is defined as a quantity of matter or a region in space chosen for study.
The quantity of mass (or region space) is mostly subjective and chosen based on the problem at hand to be solved.
Also, it is important to note that there exists a real or an imaginary surface that separates the system from its surroundings and it is known as a boundary.