The difference between cryptocurrency and regular currency is that the former is a decentralized, digital currency that's not controlled by any one person or government. The latter is a centralized, physical currency that's controlled by a single entity.
Cryptocurrency is not backed by any country, but it can be exchanged for goods and services in places where it's accepted. It also can be used to make purchases online. Regular currency, on the other hand, can only be used in countries where it's accepted as legal tender.
Cryptocurrency has no intrinsic value—it's just data stored on a computer system—but it does have an exchange value based on how much people are willing to pay for it at any given time. Regular currency has intrinsic value because it represents something tangible—like gold or silver—which could be traded for goods or services even if there weren't any other currency in existence anywhere else on Earth right now (but there wouldn't be).