Can someone explain this money concept to me? How is this possible?

I just talked to my grandfather in Latvia (European country) and he told me that the dollar is still worth the same in terms of the Latvian currency (lats) as it was around 5 years ago. I asked him why and he said it is because the lat is backed by the U.S currency, yen (Japanese currency) and Euros. Can someone explain to me how to dollar is still worth the same in lats, despite the inflation?