The difference between an open and a closed system has to do with the flow of matter and energy into and out of the system. Here's a brief explanation of each:

1. Open system: An open system is a system that can exchange both matter and energy with its surroundings. In an open system, matter and energy can enter or leave the system, and the system can change as a result. An example of an open system is a pot of boiling water on a stove. The water and steam can escape the pot and energy in the form of heat is being added from the stove.
2. Closed system: A closed system is a system that can exchange energy, but not matter, with its surroundings. In a closed system, energy can enter or leave the system, but matter cannot. An example of a closed system is a sealed container of gas. The gas molecules can move and exchange energy with the walls of the container but cannot escape it.

The distinction between open and closed systems is important in many fields, including physics, chemistry, and engineering. It allows us to understand how systems interact with their surroundings and how they can change over time.