Bitcoin is not a currency, Bitcoin is money.
Money is that which can perform all three functions of money, a store of value, a medium of exchange, and a unit of account.Currency arose because gold could not function effectively as money and could not perform all the functions of money.These currencies served primarily as a medium of exchange, making transactions easier, but they did not fully serve as a reliable store of value.
Here, watch this video explaining the difference between currency and money.
https://www.youtube.com/watch?v=X2uAZLjyGpM

If you go a bit deeper down the rabbit hole, you’ll realize that Bitcoin is the first true money humanity has ever had. Even gold was not good money,it couldn’t function effectively as money and eventually failed, which is why bank and fiat currency, emerged.
Bitcoin is the first real money ever.