Gold filled is 5% 14kt gold bonded to 95% metal alloy (jewelry brass). Highest grade metal in the market and closest to solid without the price tag. Worry and hassle free. Hypoallergenic and water friendly to add.
Sterling silver is an alloy of silver that contains 92.5% pure silver and approximately 7.5% copper, nickel or zinc. Hypoallergenic and water friendly.
Less than 1% gold that is bonded to the metal alloy (jewelry brass). It's more of a finish to a metal, think of it a as garment dyed but in metal form.
Tarnish occurs naturally when certain metals are exposed to air and moisture. You can polish your sterling silver jewelry with a polishing cloth and it will return to its original luster and shine.
Do not polish oxidized surfaces (darker metal parts), it will remove the patina. Rather, clean the jewelry gently in warm soapy water.
Since tarnishing is a natural process, it will happen eventually. However, you can slow the process down by keeping your jewelry away from humidity, chemicals, hair spray, and perfume, so put on your jewelry after your perfume. Try to keep your jewelry out of the bathroom, shower, kitchen and hot tub*. It also helps to store your jewelry in plastic bags with non-tarnish jewelry paper.
Chlorinated water can damage and ruin your jewelry, so remember to remove all jewelry before going near any chemically treated water.
If you want to keep your jewelry clean and shiny, you can hand polish it with a polishing cloth. You can find them at regular stores where jewelry is sold or online at Amazon or Target.