Computers store information in what is called Binary. Binary is a method of counting. Humans commonly count using base-10 or Decimal.
Decimal means that we count in groups of 10. We start at 0, and with each added digit we go up: 0,1,2,3,4,5,6,7,8,9 When we get to the next number in the sequence (ten), we add a place holder which represents our counting to ten to the left, and reset the number on the right to zero: 10
In Binary, you only count up twice for each placeholder. So where "10" in decimal represents the number ten, in binary "10" represents two.
So here's why that's important:
Computers use blocks of numbers to represent other things. Starting with the smallest block of data, a byte, which is made up of eight binary digits: 0000 0000
That byte can be used to represent a character on screen. For instance, the letter "A" is represented by the byte: "0100 0001" "B" is represented as "0100 0010"
The relation is standardized under the American Standard Code for Information Interchange, or ASCII.
Not only letters can be represented. Additionally, you can represent colors, pictures, or sound. All data in a computer is ultimately stored in binary, using zeroes and ones.