An electrolyte is an ionic compound that is either molten or dissolved in water. Both conditions let the compound conduct electricity, because in either state the ions are free to move and carry charge.
In a solid ionic compound, the ions are held in fixed positions in a lattice by strong electrostatic forces, so the solid does not conduct. Melting the compound, or dissolving it in water, frees the ions. Sodium chloride solution and molten lead bromide are both electrolytes. Solid sodium chloride is not.
Covalent compounds such as sugar do not contain ions, so they are not electrolytes even if they dissolve. A copper wire conducts because of its free electrons, but it is a metal element, not an ionic compound, so it is not an electrolyte.
