Generally plating is the process through which a piece of jewelry made from a certain metal or alloy is covered with a layer of another metal.
Gold plated metal.
With costume jewelry the base metal would contaminate the tanks with the gold in them so a different metal is plated prior to the gold plating.
In a gold plated jewelry item the metal beneath the gold plate will eventually come to the surface and become discolored so it will need to be polished.
Gold plated items have a base metal underneath the gold plate like copper or silver which makes the jewelry piece stronger and less likely to bend though these jewelry metals tarnish.
This process was invented by an italian chemist luigi brugnatelli in 1805 the first person to plate a thin coat of gold onto silver.
Due to the nature of gold plating you may need other solutions or accessories depending on what metal or item you are working on.
Additionally this step is used when the base metal like copper is known to atomically migrate outside of the gold layer to create spots of tarnish after plating.
Gold plating is a process where a thin layer of gold is bonded onto a base metal.
For example a copper or silver ring with a layer of gold on top would be sold as gold plated.
An all inclusive kit is ideal.
For more traditional methods often used for much larger objects see gilding.