What is the difference between Plated and Filled wire?

I am a “Visual” person, so I will explain using these pictures          (Not to scale)

Gold or Silver                                             Gold or Silver Filled                                                   Gold or Silver Plated                                    Depends on Karats                                    5% Gold or Silver layer                                              0.05% electroplated                                 High Quality                                              Good Quality                                                               Less Quality                                               Daily Wear                                                 Daily Wear with Care                                                  Occasional Wear with Care                 Lifetime wear                                            Decades or Lifetime wear                                          Months to a couple years             Expensive                                                  Affordable                                                                   Inexpensive                                                                                                                          Minimal abrasives & chemicals                                No exposure to water, heat,                                                                                                                                                                                           abrasives or Chemicals

Gold Karats are dependent on the “mix” of metals in the gold. Example would be that 14K gold is typically 58% gold, with a percentage of Silver, Copper and Zinc mixed in. As the Karat goes up, the higher percentage of Gold is. Remember that Gold is a soft metal and to increase durability, needs to be mixed with other metals to harden it for daily wear. (14Kt Rose Gold is also 58% gold, but the ratio of the copper to the silver is higher to give the color)

The Filled Gold or Silver is layered over jeweler’s brass and can also be labeled with 12KtGF, or 14KtGF. But it must by law contain at least 5% of gold or silver to be legally sold as such. And the label is to include that it is Gold Filled or Silver Filled or Stamped 14ktGF as an example.

I find that Gold Filled wire an affordable alternative to Gold wire (now at approx. $1800 to $1900 per ounce) with the same look. The difference between Silver Filled and Sterling silver is not nearly as big a financial gap and my preference is to not offer Silver Filled jewelry unless requested.

Sterling Silver is usually stamped 925 (92.5%) and Fine Silver is usually stamped 999 (99.5%)

Vermeil is Gold Filled layered over Sterling Silver instead of brass.

Gold or Silver Plated is usually over Copper or Brass or Nickel. Nickel can cause allergy reactions so isn’t used as frequently now but is still around so look for “nickel free”.

And then, there are other metals such as Stainless steel and Titanium that come in wire as well. These metals cause less allergic reactions.

Many silver or gold plated wires covering copper/tin come labeled "tarnish resistant" is covered with something similar to clear nail polish, which also increased it lifetime. But note that any abrasives or chemicals or a polish cloth treated to "shine" your jewelry will remove this protective coating. 

I am not an expert, but as a person who makes and sells jewelry, I am required to know the above and it can be validated upon research.

Hope you found this information helpful and I am happy to send you to other resources for more.