Loudness and Volume

Just read an article in Just Jukin about adding loudness control to
volume control circuit.

I'm not quite sure exactly what the difference is here. Is this meant
to keep the same sound level on all records played?

I do notice on my RO1454 some records are much louder than others, so
maybe this is what it is for. If so, can this type of circuit be
added to my box?

Thanks,
Mike