An electronic circuit that accepts and processes binary data (on/off) according to the rules of Boolean logic (AND, OR and NOT). See chip
and Bebop to the Boolean Boogie
A digital circuit can be conceptualized as a mass of plumbing. The circuit paths are the pipes, the transistors are the valves and the electricity is the water. Imagine opening a valve, and the water that passes through and down a pipe will eventually reach a second valve, causing it to turn on, allowing water in another pipe to flow through it that reaches another valve, and so on.
A resistor can be viewed as a large pipe that narrows into a smaller pipe, a capacitor as a storage tank and a diode as a one-way valve, allowing water to flow in only one direction.
From Logic to Plumbing
It would be a plumber's worst nightmare to have to follow the maze of pipes (circuits) that are in a chip. This simple circuit, which adds one bit to another, resides in every computer. To trace the flow of electricity through this circuit yourself, see half-adder