What is money? And why do they lose their value every year?

Let me google that for you (http://lmgtfy.com/?q=define+money)

Inflation

Not all money loses value, I have some silver dollars from the 1800's that gain in value each year.

My Chinese money, while not a large gain, gained in value, as compared to the USD, for the past two years.

And loses value, compared to what?