3 Answers

Dimmer switches save electricity, if the light is dimmed, just like switching to a lower wattage bulb saves electricity.
Very old dimmers used resistance to dim the light. They were used extensively in theaters and were known to produce a lot of heat. Heat is a waste of power. Variable transformers have also been used, but they were also watt wasters.
Modern household incandescant dimmers reduce the visible light and save energy by turning the electricity on and off very rapidly (120 times per second). It's so fast that people don't notice it and light bulb filaments don't mind it.
Dimmers are available for some flourescants, but it's a special ballast, a special dimmer and a very special price.
The same criteria apply to low voltage lights and dimmers.

Not realy,the risters in the dimmer switch,obsorbs the current when the,lamp is dimed,

Yes, if you keep it dim most of the time, doesn,t save a great deal though.