What is Salt bridge . Please explain

A salt bridge is used in electrochemical voltaic cells. A salt bridge is usually an inverted glass U-tube that connects two beakers together. The salt bridge is filled with a solution of salt; potassium nitrate (KNO₃) is frequently used as the salt. Other salt bridges may be filter paper that is saturated with potassium nitrate. The U-tube is plugged on both ends with glass wool or porous plugs. The salt solution does not interfere with redox reactions that take place within a voltaic cell.

Let us use for example the voltaic cell: Zn|Zn²⁺||Cu²⁺|Cu

If the Cu²⁺ ions come in contact with the Zn electrode, the cell would short-circuit. The salt bridge prevents this from happening by completing the circuit. In a way, the salt bridge acts as a screen. As the current is drawn from the cell, metal from the left-hand electrode (anode) loose electrons and go into the solution. The electrons travel through the external wire to the right-hand electrode ( cathode). Here the metal ions take electrons and deposit them as metal. The salt solution in the salt bridge uses its own anions (NO3-), and its own cations (K+) to substitute for the change in charges at the anode & cathode.