Question: My brother sometimes mentions electrolytes before he gose mountain biking and that he eats or something so what are thhey?

Eva Weiss answered on 10 Nov 2015:

Electrolytes are basically salts. When put in water, the solution conducts electricity because the salt falls apart into ions – electrially charged particles.
When your brother talks about taking electrolytes, he means to replenish the ones he uses while sweating. Sweat is salty just like tears. People believe that if you work out and sweat a lot you need to drink something that contains the salts that you lost. These salts are important for your body to function. They are involved in communication between and within the cells our bodies are made of. For example. in order for a muscle to contract certain ions like sodium and potassium need to be present. Otherwise the person could get weakness or cramps.