An electrochemical cell is made up of two half cells connected by an external conductor and a salt bridge. the function of the salt bridge is to

To permit the migration of ions

In the electrochemical cell, electron flow from anode to cathode. for the process to continue there must be some mean to keep the charge in balance. the salt bridge maintains the neutrality of solution. the salt bridge does not let the electrons move from the electrolyte. it makes the circuit complete and hence allows the flow of current. some of the examples of salt bridge are KCL, KNO₃ etc.