I posted the following here:
[Source:] p 5 of 26, by Dr Darrell Larsen
Here is an analogy involving letters:
To phonetics, these are all slightly different, as their forms are not identical.
To phonology, these are all the same, since, psychologically, they all represent the letter .
(Disclaimer: phonetics and phonology aren’t concerned with letters at all , only with sounds. This is just an analogy .)
This rudimentary analogy may also help.