A wedding anniversary is the anniversary of the date a wedding took place. Traditional names exist for some of them: for instance, fifty years of marriage is called a "golden wedding anniversary" or simply a "golden anniversary" or "golden wedding".

The historic origins of wedding anniversaries date back to the Holy Roman Empire, when husbands crowned their wives with a silver wreath on their twenty-fifth anniversary, and a gold wreath on the fiftieth. Later, principally in the twentieth century, commercialism led to the addition of more anniversaries being represented by a named gift.

In Australia, where one can receive a letter of congratulations from the Governor-General on the 50th and all subsequent wedding anniversaries; the Prime Minister, the federal Opposition leader, local members of both state and federal parliaments, and state Governors may also send salutations for the same anniversaries.

In Canada, one can also receive a message from the Governor-General for the 50th anniversary, and every fifth anniversary after that.

In the United States, a couple can receive a greeting from the President for any wedding anniversary on or after the 50th.

Roman Catholics may apply for a Papal blessing through their local diocese for wedding anniversaries of a special nature (25th, 50th, 60th, etc.).

More Info: en.wikipedia.org