Arbitrage Relationship Between Spot rates, Forward Rates, interest Rates?

The percentage difference between forward and spot exchange rates is approximately equal to the percentage difference between the 2 countries interest rates. i did not quite well understand this concept. Can anyone explain this , preferably with an example as well? thanks.

I wrote an article on covered interest rate parity that may be helpful here: http://financialexamhelp123.com/covered-interest-rate-parity-irp-pricing-currency-forwards/