What is an Electrolyte ?

An electrolyte is a solution which consists of ions which facilitate conduction.  A solution of sodium chloride in water is an example of an electrolyte.  The sodium  and the hydroxyl ions conduct electricity.  This form of conduction is called ionic conduction which is different from the electronic conduction in metals.   

In Electrical Engineering, Electrolytes are important parts of batteries and in the process such as lectroplating and electro refining. 

Salts when melted can also be called electrolytes.  Sodium Chloride when heated above its melting point conducts electricity in the molten state.  

Electrolytes are classified into strong electrolyte or weak electrolytes depending on the concentration of ions in the solution.