An exchange rate is the price of a nation’s currency in terms of another currency. It’s a value of exchange between the two currencies in question.
Whilst you’re abroad it’s useful to download a currency converter on to your phone to work out how much everything would cost back at home, it also avoids you being ripped off if someone is trying to charge you too much for a product because the currency converters will show up to date rates (wifi dependent). A free site is XE.com, the site also has a free app too.
Please note shops and eateries in other countries can decide their exchange rate, so don’t be surprised if prices are slightly different to your calculations.
At your time of travel, Money Saving Expert will be able to tell you which bank or travel desk provides the best exchange rate.