We have seen that the binary code uses only two SYMBOLS to represent any quantity, symbols that are "0" and "1".
Well, only two symbols are VERY EASY to represent with the tools that are available in a Computer: electricity, switches, etc ...
In computers there are electronic components that may or may NOT have "current". These "currents" are also easily measurable, also because we are not interested in a precise measure, but only know if there are or are not there.
If there is current the value of the binary code is "1", if the current is not there then the value is "0".
(I used the term "current", because it is the one with which generically indicates the presence or absence of electrical phenomena, for the accuracy I tell you that the value that is measured, in reality, is that of a continuous tension: at the beginning such voltage assumed the values of +5 Vdc (5 volts in direct voltage) and 0 Vdc or even + 5 Vdc and - 5 Vdc, to indicate respectively "1" and "0", today we also use lower voltages, so we save energy... and the PC consumes less)
The same concept, given the ease of representation, is applied, more or less, to each component that needs to store data. For example an hard disk: the heads read magnetic charge values, present, or NOT present, in certain areas of the surface of the disc plates.