Melting Point
893 °C

Composition
Sterling silver is an alloy of 92.5% Silver and 7.5% of another metal, usually Copper.

History
Sterling Silver is thought to have originated in Europe in the 12th Century. The origin of the word Sterling however is still in doubt. The word is thought to have originated some time during the 12th and 13th centuries.

Alloys
Put simply, an alloy is a mix of two metals. In the case of Stirling Silver we have two solid state metals combining to form the alloy.
Alloying one metal with another often enhances its properties. In the case of Sterling Silver, alloying the silver with copper enhances its strength.
Fine silver (99.9% pure) is generally too soft for producing such objects as pendants and therefore, the silver is usually alloyed with copper to give it strength

Further Reading
To read a little more about Sterling Silver, take a look at the detailed description from Wikipedia, the free encyclopedia.
Melting Points of Metals and Alloys