What does 925 on the back of earring mean?

925 is a common hallmark used to indicate that jewellery is made of sterling silver. The hallmark represents the percentage of pure silver contained in the alloy - in this case, 925 indicates that the alloy contains 92.5% pure silver and 7.5% alloying metals, typically copper. This ratio gives the metal durability and strength while retaining the valuable properties of silver such as being tarnish resistant and relatively lightweight.

Jewellery often made of 925 silver includes earrings, necklaces, bracelets, rings and other body jewellery.