Hard Water and Soft Water

What is the taste of "HARD" water?  and why is limescale building up in my water kettle ?
Pure water does not exist in the natural world. Naturally occurring water has any number of things that water has picked up from it's travels over, on and in the earth. The various minerals that dissolve in water make it "hard". 

Hard water typically has the following characteristics:

• Bathing with soap in hard water leaves a film of sticky soap curd on the skin. The film may prevent removal of soil and bacteria. Soap curd interferes with the return of skin to its normal, slightly acid condition, and may lead to irritation. Soap curd on hair may make it dull, lifeless and difficult to manage. Soaps will leave behind a scum both on the surface of the water and also on whatever is being washed, including your skin and hair. This scum on the surface of things is typically what makes the squeek in "squeeky clean". It's not a good thing.

• Flavors - Coffee, tea and other products that are used to flavor water will not dissolve as readily in hard water.
• Laundering - Clothes washed in hard water often look dingy and feel harsh and scratchy. The hardness minerals combine with some soils to form insoluble salts, making them difficult to remove. Soil on clothes can introduce even more hardness minerals into the wash water. Continuous laundering in hard water can damage fibers and shorten the life of clothes by up to 40 percent.
• Problems in Water Boiler Systems and Pipework - Hard water also contributes to inefficient and costly operation of water-using appliances. Heated hard water forms a scale of calcium and magnesium minerals (limescale deposits) that can contribute to the inefficient operation or failure of water-using appliances. Pipes can become clogged with scale that reduces water flow and ultimately requires pipe replacement. Limescale has been known to increase energy bills by up to 25%
• Hard Water is Not dangerous
• Hard water is not dangerous and not a health risk. In fact, the National Research Council (National Academy of Sciences) states that hard drinking water generally contributes a small amount toward total calcium and magnesium human dietary needs. They also state that in some instances, where dissolved calcium and magnesium are very high, water could be a major contributor of calcium and magnesium to the diet.
• The ideal solution would be to leave the calcium in the water, but alter its state so that it couldn't form limescale. This is what magnetic water conditioners aim to achieve but, although they do work for some people, the science behind them is not fully understood.