Sterling silver is composed of 92.5% silver alloyed with copper to strengthen it. Silver has one of the highest reflectivity of any metal, giving it unmatched brilliance, making it perfect for jewelry designs. Silver also has extremely high electrical conductivity and thermal conductivity. Despite all these wonderful properties silver is relatively abundant and easy to extract from ore, so it is, at the same time, relatively affordable making it ideal for jewelry that will appeal to a wide audience.
At various time in history silver was even more valued than gold and had a mystical allure to it, often being associated with the sea, moon and lunar goddesses. Hallmarking of silver places a stamped mark on the silver to identify its origin and purity and is often an important part of determining the value of a collectible piece.
There are other alloys of silver with a higher content of silver than sterling. Mexican and Britannia silver each have about 95% silver. Coin silver on the other hand typically has only 90% silver.
  
   The cleaning of sterling silver can be a burdensome task, which is why much of the silver jewelry manufactured today has various types of anti-tarnish finishes ranging from a flash overlay of pure silver, waxes, proprietary coatings and the currently very popular rhodium plating. Rhodium in fact is a much more expensive raw material, but does not have quite the high brilliance of silver, however its superior anti-tarnish property outweigh its lower reflectivity value.
Silver in its pure form will not tarnish but is too soft for use in jewelry. Sterling silver will tarnish. This is not a defect but the result of a natural chemical process that occurs when sterling silver is exposed to chemicals in the air. Other common tarnish causing elements are wool, rubber bands and latex gloves. Humid environments will accelerate tarnishing.
Tarnish is easily removed when first notice as a yellowish tint but will become more difficult to remove as it turns brown and black. At this point it will require professional cleaning and/or harsher chemicals that can harm your jewelry.

Storing your sterling silver in the open air and humidity for extended periods of time can cause it to tarnish quickly.  Tarnish first appears as a golden hue on your sterling silver then quickly turns to black.  This is a normal process that is caused by oxidization and moisture from air and believe it or not sunshine. To keep tarnish to a minimum it is advised that you store your jewelry pieces when not wearing them. 

Although your jewelry is scratch resistant it isn't scratch proof, so we recommend that you store your jewelry so that it isn't rubbing up against other articles, like in a loose drawer or jewelry box.   Also, when storing remember that exposing it to air promotes tarnishing, so use the zip lock bags to protect from scratches and tarnish. 

Avoid storing your sterling silver jewelry directly on wood surfaces, because wood usually contains acids that can mar the finish.  Oak seems to be the worst for this.  Also, avoid storing your sterling silver with other metals, like pennies, and rubber, these too cause tarnish and damage.