In thermodynamics, systems can be classified based on their interactions with the surroundings. An open system allows for both energy and matter to exchange with the surroundings, like a beaker containing reactants. A closed system, on the other hand, permits energy exchange but restricts matter exchange, like a sealed vessel where reactions occur without additional matter entering or exiting. Finally, an isolated system does not exchange either energy or matter with the surroundings, for example, a thermos keeping a reaction contained. These classifications help in understanding how energy is transformed and conserved in thermodynamic processes.