Electroplating involves the deposition of a layer of metal on top of another metal. Often the silverware you see on dinner tables is cheap iron coated with a thin layer of silver. This is done by a process called electroplating in an electrolytic cell.
As is shown in the animation on the right, the metal we wish to coat is placed on the negative terminal of the power source. This is then immersed in an electrolyte that contains ions of the metal we wish to coat with, in this case, silver ions. To the positive terminal we connect a silver metal.

Electrons are pumped out of the silver metal in effect corroding it and releasing silver ions into the electrolyte solution.

Ag_(s) => Ag⁺_(aq)+ e

The positive ions migrate over to the negative electrode (the metal we wish to coat) and regain their electrons to form silver metal once again.

Ag⁺_(aq)+ e =>Ag_(s)

The ions that migrate are not always the ones that have just being released from the silver metal but may be any silver ion in the electrolyte. The ions that are released from the silver metal just replace the ions that have been taken out of the solution. A constant silver ion concentration is maintained.

Give the polarity and the reaction that occurs at the cathode.
Give the polarity and the reaction that occurs at the anode.

Electroplating is not as simple as the animation above shows. If we were to coat a piece of iron in this manner a loose black sludge would develop. In practice the voltage, current, temperature and electrolyte are carefully controlled.

Looking at the animation above it is easy to see the relationship between number of atoms of silver deposited and the number of electrons that pass through the circuit.

This relationship is very important and leads us into the next chapter where we can calculate the mass of metal deposited given the current supplied.