But is it differs from fiat digital currencies in several important ways?
It is the first currency and payment system. In the past, you need a third party to send money.
Bitcoin has broken the need for a third party, it is decentralized and therefore does not need a central bank to guarantee the currency.
I hope you visit Andreas Antonopoulos's
[1] page for more information.
[1]
https://www.youtube.com/channel/UCJWCJCWOxBYSi5DhCieLOLQ