A water softener does one thing: it removes calcium and magnesium ions from the water, replacing them with sodium ions in roughly equivalent quantity. The chemistry is straightforward. Each calcium ion (2+ charge) leaving the resin releases two sodium ions (1+ charge each) to balance the charge. The total ion count goes up slightly; the total mineral mass shifts from calcium-and-magnesium to sodium.
How much sodium
For a typical Indian residential setting — feed-water hardness 300 ppm — softening adds roughly 70 mg of sodium per litre of water. By comparison, a teaspoon of table salt contains about 2,300 mg of sodium. A glass of softened water contains less sodium than a slice of bread. The dietary impact for almost everyone is negligible.
The two exceptions are infants on formula and adults under strict low-sodium prescription. Both groups should drink reverse-osmosis-treated water, not softened water, because the RO membrane removes the added sodium along with everything else. This is one reason a kitchen-tap drinking-water system is recommended alongside whole-house softening — softening for bathing and washing, RO for drinking and cooking.
What the shower actually feels like
Soft water does feel different in the shower, and the difference is sometimes described as "slippery". The slipperiness is real but it is not soap residue or sodium. It is the absence of the calcium-soap precipitate that hard water leaves on skin. On hard water, soap reacts with calcium to form a sticky film that the rinse never fully removes — the squeak you have learned to interpret as "clean" is the squeak of that film. On soft water, the soap rinses away completely. The skin feels softer because nothing is left on it.
The "squeaky clean" feel of a hard-water shower is the feel of soap residue. The "slippery" feel of a soft-water shower is the feel of skin without residue.
What softening does not do
Softening removes hardness. It does not remove iron, chlorine, TDS, sediment, or organics. A homeowner who installs only a softener on a feed with iron will get a softener that fails inside a year. A homeowner who installs only a softener on a feed with chlorine will get a slightly less chlorinated shower but no taste improvement at the drinking tap. The softener is one stage in a treatment train, not the whole train.