Thusly "NetMax" Spake Unto All:

TDS is a (roundabout and ambiguous) measure of the electrical
conductivity of a water, which in turn is a measure of the salinity of
the water.

I think your intro is reversed, it should read:
"Measuring the electrical conductivity of water is a roundabout method of
determining the level of TDS."

I don't really see that. I mean, yeah, it's good to know the
conductivity of the water, and yeah, the conductivity is dependent on
the amount of dissolved salts.
I just question the use of measuring conductivity but expressing it as
fictional milligrams of the wrong salt per liter. I really don't see
the point.