Electrolytes are minerals in your body that have an electric charge. They are in your blood, urine, tissues, and other body fluids. Electrolytes are important because they help

Balance the amount of water in your body

Balance your body's acid/base (pH) level

Move nutrients into your cells

Move wastes out of your cells

Make sure that your nerves, muscles, the heart, and the brain work the way they should.

Sodiumcalciumpotassium, chloride, phosphate, and magnesium are all electrolytes. You get them from the foods you eat and the fluids you drink.

The levels of electrolytes in your body can become too low or too high. This can happen when the amount of water in your body changes. The amount of water that you take in should equal the amount you lose. If something upsets this balance, you may have too little water (dehydration) or too much water (overhydration). Now, these natural minerals can be exerted when doing physical activity most prominent in endurance athletes such as marathon runners or cyclists. It is extremely important to replace these exerted minerals to keep balance in your body if it is not balanced you will not be able to perform at the highest output. 

This can be aided through supplementation there are plenty of products that provide this such as Powerade, Gatorade, C4 energy drinks and powder for supplementation from Optimum nutrition.