It's common to say that computers work in binary numbers, that bits are like binary numbers, and that everything in a computer is binary, but after all, what are these binary numbers? How do they work? What does the word binary mean? And what is the difference between binary numbers and the decimal numbers that we normally use?
Binary numbers, or numbers of base 2, are numbers written with only two digits, 0 and 1, such that each decimal place, or rather, binary place is added to the left just after the number 1, and not after the number 9 the way it works in the decimal system we normally use. That is, in binary, we count: 0 (zero), 1 (one), 2 (two), 3 (three), 4 (four), 5 (five), 6 (six), 7 (seven), 8 (eight), 9 (nine), 10 (ten), and so on.
The term "binary" is related to the number "two." In this case, it's about the fact there are only two digits possible (0 and 1). Similarly, "decimal" means "ten" and we have ten possible digits (0123456789). There are others beside these, like hexadecimal, with 16 digits (0123456789ABCDEF).
Each system may also be referred to by its base: binary is base 1, decimal is base 10, hexadecimal is base 16. A number of base X with N places has a maximum value of X to the Nth power minus 1. For example, the maximum of 3 decimal digits: 999, equals 103 - 1. The maximum of 8 binary digits is 28 - 1, or 255 (11111111). Observe that, in an exponentiation such as 28, we call 8 the exponent or power and 2 the base.
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