There are generally 3 types of terms you will hear when describing silver: sterling silver, pure silver, and silver plate.
Sterling silver and silver are often described as the same, but are not. Sterling silver is an alloy of silver. Pure silver, usually called fine silver, is made of entirely silver, and nothing else. Sterling silver consists of approximately 92.5% silver, and the remaining 7.5% is other metals. The reason sterling silver exists is because pure silver is too soft, does not hold its shape well on its own, and cannot be used to make daily use items that get beat around. With sterling silver, metal experts add other metals like copper, steel, or iron to fortify the toughness of the silver. This allows it to withstand daily use in various items.
Sterling silver easily loses its luster in many situations. In the case of pure silver, it will not tarnish on its surface because tarnish is more responsive in alloy metals. To test the tarnish tendency of a metal or alloy, you simply have to rub your finger tightly over a shiny piece of your sample material. With sterling silver, you usually find some dull smudges on your skin. Nevertheless, you can keep your sterling silver items shiny by using a cloth or cotton to regularly and gently clean its surface. If you do not use your sterling silver items for a prolonged period of time, you may notice that tarnish starts to appear. American-made Sterling silver is always marked Sterling or 925. There are no exceptions to this rule. Be keenly aware of fake sterling silver from China that is erroneously marked as sterling or 925.
Silver plate is the process of bonding an extremely thin layer of silver to a base metal; most commonly used metals are copper, brass, or nickel. This layer of silver is very thin and nearly impossible to recover from the item. Silver-plated flatware and hollowware are common and inexpensive. If your jewelry has EP, EPNS, Silver on Copper, or other terms marked on it, then it is electroplated silver and not sterling. EPNS stands for electroplated nickel silver. Manufacturers are not allowed by law to use the word “sterling” on plated items, so you will never see the term “sterling plated”. However, some unscrupulous sellers, often seen on TV, will use the term “layered in precious sterling silver”. This is an advertising ploy used to get you to buy their product, thinking it is sterling silver. It is not sterling.