Sterling Silver
Sterling silver is a metal alloy of silver containing 92.5% pure silver and 7.5% other metals, usually copper. As the purity of the silver decreases, the problem of corrosion or tarnishing also increases. Sterling Silver does not react with oxygen or water at ordinary temperatures, so does not easily form a silver oxide. However, the other metal in the alloy, usually copper, may react with oxygen in the air. Hand Polishing is the method of care adhered to by serious silver items collectors, as it brings out the beautiful luster of the sterling silver without destroying its patina. There are a variety of products available for hand polishing from pastes to creams, some examples such as Wright's Silver Cream and Twinkle Silver Cream. These are readily available through some supermarkets and jewelry stores.
Please don't wash your sterling silver and stainless steel together. Chemical reaction may occur if they touch together, resulting in black spots on the sterling silver. Use a mild dishwashing liquid, and don't apply undiluted dishwashing liquid directly to sterling silver. Detergents containing phosphate can turn sterling brown.

Costume Jewelry
Costume jewelry or Fashion jewelry is jewelry that is made of less valuable materials, including base metal alloy, glass, plastic, and synthetic stones, in place of more valuable materials such as gold, silver and gems. Costume jewelry is most flashy products as opposed to fine jewelry and main use in fashion. Costume jewelry was made of inexpensive simulated gemstones, such as rhinestones or lucite, set in pewter, silver plated nickel or silver plated brass.
Modern costume jewelry incorporates a wide range of materials. High end crystals, CZs or cubic zirconia simulated to diamonds, and some semi-precious stones are used in place of precious stones and metals include gold or silver plated brass. Lower priced jewelry may still use gold or silver plating over pewter, nickel or other metals.

Silver Plated
Silver plating is a method of depositing a thin layer of silver onto the surface of another metal alloy, most often materials as pewter, copper or brass. Silver plate was used to provide a cheaper version of items that might otherwise be made of sterling silver, including cutlery, costume jewellery and candlesticks.

Stainless Steel
Steel is an alloy consisting mostly of iron, with a carbon content between 0.02% and 1.7 or 2.04% by weight, depending on which grade. Stainless steel is defined as an iron-carbon alloy with a minimum of 10.5% chromium content. The name originates from the fact that stainless steel does not stain, corrode or rust as easily as ordinary steel. Stainless steels have higher resistance to rust and corrosion in many natural and man made environments. However, it is important to select the correct type and grade of stainless steel for the particular application.

Some grades of Stainless Steels:

Type 301 — Highly ductile for formed products. Also hardens rapidly during mechanical working. Good weld ability and better wear resistance and fatigue strength than type 304.
Type 304 — The most common grade; the classic 18/8 stainless steel, most for food and surgical stainless steel uses.
Type 316 — The second most common grade after 304; Alloy addition of molybdenum prevents specific forms of corrosion. 316 steel is used in the manufacture and handling of food and pharmaceutical products where it is often required in order to minimize metallic contamination. It is also known as "marine grade" stainless steel due to its increased resistance to chloride corrosion compared to type 304. Most watches and costume jewelry that are made of stainless steel are made of Type 316L.

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