Plating - Placage [French] {plakaʒ} - Listen French pronunciation   Plating is a process whereby one metal is covered by another, it's a good way to obtain certain property of the plating metal without having all the part in said metal.
Mainly for decorative purpose, plating is also useful to reduce corrosion.
Plating is the name of the process in general, but is often used to talk about electroplating and most often for gold electroplating.
Plating can be done by various methods, like liquid coating, powder coating, Physical Vapour Deposition (PVD, see the definition), Chemical Vapour Deposition (see the definition).
Alongside plating you'll often encounter the term "wrapping", mainly encountered in the rep world, this term refers to the gold filling process as known in the jewellery word.
The difference between wrapping or filling and plating resides in the method and result even though the appearance won't change between the two.
Wrapping or filling whether it be gold or any other material, is the deposition of multiple sheets of material on top of the base metal, it requires a lot more of the precious metal and offers a more durable product. This is a mechanical process.
Plating is only depositing a very thin layer of material on top of the base, just to give the colour and some protection. This is a chemical process.
Even if technically there's no limit to the thickness of an electro-plating, it will usually be used to put the thinnest layer possible, whereas wrapping/filling is usually thicker.
You'll eventually hear the word Vermeil when talking about plating, it's simply when the plated material is silver and the platting is at least 2.5 micron of gold.
There's no regulation regarding gold plating but there is for gold filling and vermeil.