We already know a system and surrounding is separated by a boundary and the boundary is of different types. They may be permeable boundary or adiabatic boundary or that thermal boundary and because of that matter and energy can be exchanged between the system and the surrounding. On the basis of that there are three types of systems. They are open system, closed system and isolated system. So let us understand them one by one. First of all let us understand open system. What is the meaning of open system? Open system is the system in which there is a exchange of both matter and energy between the system and surrounding. Exchange of both matter, matter and energy. So there is exchange of both matter and energy in case of open system. Let me explain that with a diagram. Suppose this is the system part and around it obviously there is surrounding. Yes. Now here it is, this is the boundary right. Now let us consider this boundary is permeable. This boundary is permeable. And this boundary is permeable that means anything can be exchanged. So matter as well as energy will be exchanged or they will either get or they will either gain or they will either lose with the surrounding. They will directly exchange matter and energy with the surrounding. An example of that might be if you take hot water in a cup or a glass. Then what will happen? Some time some matter that will amount of water is evaporated and the volume of water decreases and energy also gets transmitted. That means hot water gets converted into a cold water. So in that particular case matter as well as energy has been exchanged. So that is called open system. And in this type of system the boundary is permeable. That means anything can be exchanged. Number two is closed system. Closed system. This is the type of system in which only energy gets exchanged but matter do not get exchanged. Let us take an example. If the boundary here, if the boundary here is diathormal. Diathormal. That means it can only lead the system to exchange its energy but matter will not be exchanged. An example of that is if you take a bottle, water bottle and if you put one liter of water in that and if you leave it in sunlight then what will happen? After some time it will gain some heat energy but is the matter changing? Will the volume of water decrease or increase? No. The volume remains the same only the temperature is changing. That means only the heat energy is being exchanged but matter is not exchanging. So that type of system is called closed system. That means only heat is exchanged and matter remains same. Matter remains same. That is the matter is not exchanged between the system and surrounding. And the last one is isolated system. It is clear from the word. That means it will not exchange anything with the surrounding. It will either exchange energy nor matter. Either energy nor matter, matter is exchanged between the system and the surrounding. And in this particular case the wall will be adiabatic. That means it will not lead anything to change. An example of that is if you put hot water in a thermosplast then what will happen? After some time as well the temperature remains the same. In the matter do not get exchanged. So in that particular case neither matter nor energy is being exchanged. In that type of system is called isolated system. So I hope you understood about the three types of system.