Salt bridge and its importance in a cell

 salt bridge - is t U-shaped tube containing semi solid paste of inert electrolyte either KCl, KNO3 or ammonium chloride in Agar Agar or gelatin. 

Function of salt bridge -   

I) to complete the electrical circuit by allowing the ions to flow from one solution to other without mixing of the two solution 

II) to maintain the electrical neutrality of the solution in the two half cell (in voltaic cell)