With the currency pair USD/BGN we can see the difference in value between USD and BGN and current figures tell us that we need 1.77120 BGN if we're interested in buying a USD.
Going into terminology, in this case USD is the transaction currency or base currency and the BGN is the quote currency and you can also call it the counter currency.
The value of this currency pair has been changing in the last hours and the data it has left us has been a minimum price of 1.77050 and a maximum price of 1.77820 . This means that it has had a variation of -0.00620, which translated into a percentage is a -0.35000%.