Binary, also known as the base-2 numeral system, is a way of writing numbers by using only two different symbols, usually a one (1) and a zero (0). Even though this is a whole eight symbols less than we normally use (this is called decimal, or the base-10 numeral system), it's still possible to write out each and every number. While counting with only two symbols can seem pretty confusing for humans, we'll see in a minute how using binary makes a lot of sense when thinking about computers. In fact, binary is used in just about every computer on Earth and every time you've used one, you've seen binary in action.
To get an idea of how binary works, let's first take a closer look at the decimal system (remember, the decimal system, or base-10, is how we normally write numbers). What happens when we count from nine to ten?
Okay, so here's where things start getting cool. Binary works in exactly the same way! The only difference is, we only have one symbol before we "run out" and have to start using another digit. Let's try counting again, this time from zero to two, and in both decimal and binary.