HCl and NaOH react based on the following equation:
HCl + NaOH ..............> NaCl + H2O
This reaction is known as a double replacement reaction. In this types of reactions, the electrolyte (and the solvent) is water and the driving force is mainly the formation of a non-electrolyte produce.
Based on this, the driving force in the above neutralization reaction is the formation if the non-electrolyte salt (NaCl)