In computer science and mathematics, binary is a system where numbers and values are expressed 0 or 1.
Binary is base-2, meaning that it only uses two digits or bits. For computers, 1 is true or "on", and 0 is false or "off".
The binary number system is positional. So even though it only works with 1's and 0's, the position of those two digits can represent much more.
For example, here are the numbers 0 to 10 in binary:
|Decimal Number||Binary Number|
And things like ASCII work with binary under the hood.
In fact, while computers work with all sorts of different input and output, at their core, they work entirely with binary.
To get a high-level overview of how computers work and binary is used, check out this video: