Storage in computers?
Nowadays, all computers are built following certain conventions. One of those conventions is the use of zero and one (i.e. low voltage and high voltage): it's perfectly possible to make computers that don't use zeroes and ones, and in fact the Soviets did so (look into the Setun project). Another of those conventions is that text-based data comes in units of eight bits each, called "bytes".

Each byte holds a number from zero to 255, and more conventions define what each number means. The ASCII standard, for example, says that 65 means "A", while the UTF-8 standard says that 195 followed by 184 means "ø". But there's nothing intrinsically "A"-like about the number 65: it's just a convention people have agreed to follow, to make it easier for programs to work together.

(P.S. When two programs are using different conventions, you get a garbled mess called "mojibake". Nowadays most text data is stored in UTF-8, which helps avoid this, but there are still some holdouts (cough Windows API) who insist on using other conventions instead. It's a headache when you have to deal with that.)