Silver streaming is the term often used when a company makes an agreement with a mining company to purchase all or part of their silver production at a low, fixed, predetermined price to which both parties agree. The silver is usually a by-product of the mineral the mining company's business is based on (most silver is produced as a by-product of base metals). The arrangement can be made through silver purchase agreements or precious metals agreements.
The transaction is considered mutually beneficial. The mining company gets much needed capital by immediately monetizing the non core silver, while the company receiving the silver gets it without having to invest in exploration, development, maintenance. Silver streaming companies have no control over the mines that produce their silver meaning that when production falls short of expectations or is affected by political instability it must incur the losses itself; because of the lack of control over production, earnings are based entirely on the market price of silver.

Barrick Gold

Barrick Gold

Barrick Gold Corporation is the largest pure gold mining company in the world, with its headquarters in Toronto, Ontario, Canada; and four regional business units located in Australia, Africa, North America and South America...

, and Goldcorp

Goldcorp

Goldcorp Inc. is a gold producer headquartered in Vancouver, British Columbia, Canada. Goldcorp has 16 operations and development projects in 6 countries across the Americas....

 are 2 mining companies which do business with silver streamers.
Silver Wheaton Corporation

Silver Wheaton

Silver Wheaton is a pure play silver mining company, the largest in the business of silver streaming. It produces over 23 million ounces and sells over 20 million ounces of silver mined by other companies as a by product...

is the world's largest silver streaming company.