Any information can be reduced to a sequence of simple yes/no questions, called bits.
Shannon showed you can measure information exactly like a weight, in units called bits. One bit equals a single yes-or-no question. String enough bits together and you can describe a photograph, a song, or an entire book, no matter what original language was used to create it.
When you say 'yes' or 'no' to a simple question, you have chopped reality into pieces a computer can swallow. Think of an audio file: every second of music is measured thousands of times, and each measurement is a 'yes' or 'no' for a certain sound level. Just as a photo becomes a mosaic of dots, sound becomes a string of bits. But how do you know if that string is correct?
Why it matters Every file sent over the internet today is, at its core, just a long string of bits.