> [A logic gate consists in] three connections where there may or may not be some electricity. Two of those connections are places where electricity may be put into the device, and the third connection is a place where electricity may come out of the device. (Scott, 2009 p.21)
Logic gates are the basic building blocks of digital computing. **A logic gate is an electrical circuit that has one or more than one input and only one output.** The input controls the output and the logic determining which types of input (on/off) lead to specific outputs (on/off) is identical to the truth-conditions of the [Boolean connectives](/Logic/Truth-functional_connectives.md) specifiable in terms of [truth-tables](/Logic/Truth-tables.md).
Physically, what 'travels through' the gates is electrical current and what constitutes the 'gate' is a [transistor](/Electronics/Digital_Circuits/Transistors.md) responding to the current. At the next level of abstraction it is bits that go into the gate and bits which come out: binary information that may be either 1 or 0.
