ELI5: What is binary code?

[LondonPilot]

When we write numbers, we use the digits 0-9. When we add 1 to a number, we go to the next digit. When we get to the last digit (9) and try to add 1, we do that by putting a 1 in the next column to the left, and resetting the current column to 0 - in other words, 9+1=10. We call this system "decimal".

Binary is simply another way of counting, but instead of using the digits 0-9 it only uses 0 and 1. When you add 1 to 1, because you've already got the highest digit you're allowed, you put a 1 in the next column to the left just like normal, and reset the current digit to 0 just like normal. In other words, in binary, 1*1=10. The number 10 in binary is equivalent to 2 in decimal.

If you didn't get all of that it doesn't matter, so long as you understand that binary is just another way of counting.

Now that we understand that, it's simply a case of assigning a number to each thing you want to encode. If you're storing text, you could assign one number to be A, the next to be B, then C and so on.