What is inflation?

The Adam Smith Institute
"Inflation, as commonly understood, is a general rise in prices, as measured by some index, such as the CPI, RPI or RPIX. On such an understanding, high commodity prices driven by strong demand (or limited supply) are ‘inflation’. So is an increase in a sales tax (like VAT). This is what we are hearing from the Bank of England at the moment.

But is this view of inflation correct? Austrian school economists don’t think so. To them, inflation is an increase in the supply of money. Rising prices are merely one consequence of that underlying phenomenon."