Both gold-plated jewelry and gold-filled jewelry consist of a layer of gold that is bonded to another metal (often brass, copper or sterling silver). The difference is the thickness of the layer of gold and the way they are bonded.
Gold-filled jewelry has a thicker layer of gold, meaning it can stand up to everyday wear and tear. It doesn’t easily wear off and, while it can tarnish, it is less likely to do so. If it does, you can easily use a jewelry polishing cloth to clean it up.
On the other hand, the thin layer on gold-plated jewelry can be easily scratched and wears off quickly. It is also prone to tarnishing, but because of the thin layer, using a polishing cloth could actually remove the layer of gold.