You type "Hi" and the computer stores 01001000 01101001. Text is just numbers wearing a costume. Here is exactly how a string turns into binary, why UTF-8 matters, and how to do the conversion both ways in a few lines of JavaScript.
What "binary" actually means here
Computers do not store letters. They store numbers, and every number is a run of ones and zeros. Each character maps to a code point, that number becomes a byte, and each byte is written as eight bits.
The letter A has the ASCII code 65. In binary that is:
65 = 01000001
