Combinational circuits are a type of digital circuit where the output is determined solely by the current inputs, without any memory or feedback. These circuits perform various logical operations using basic components like AND, OR, and NOT gates. They are essential in building more complex systems, such as arithmetic logic units and multiplexers. In combinational circuits, the output changes immediately in response to changes in the input. This characteristic makes them different from sequential circuits, which rely on previous inputs and states. Common applications of combinational circuits include adders, subtractor circuits, and encoders.