Digital electronics are based on what are called logic circuits, which open or close based on the presence of an electronic pulse. Logic circuits are also called logic gates.
At its most basic level, digital electronics involves the passage of electronic pulses along circuitry. If the electronic pulse is present at a given circuit, this is represented by the number one. If the pulse is not present, it is represented by a zero. As such, it is an example of Boolean logic, which means that only one of two variables is true. This becomes the building block of digital circuitry.
The various logic gates have corresponding truth tables which then make up the logical basis for the resulting processes such as AND, OR, NAND (not and) and NOR (not or). Decoders are circuits with two or more inputs and one or more outputs that combine various types of logic gates. A multiplexer features two or more inputs and one output, acting like a switch that selects the input.
The digital circuitry acts to control all relevant functions. For example, when using a digital mobile phone, the voice audio input is converted by digital circuitry into a series of electronic pulses corresponding to a series of zeros and ones. The receiving telephone's digital circuitry then converts the electronic impulses back into the sound of the voice.