Bitcoin was announced in 2009, and is now the largest blockchain currency by market capitalization. Bitcoin was not the first digital currency, but it was the first digital currency based on the blockchain concept. Paypal is a virtual currency that started in 1998, but it is not a blockchain based system.
The importance of blockchain can not be overstated. In the process of settling a transaction the blockchain verifies that funds are available and prevents double-spending.
Normally, in the case of credit cards and Paypal, a central authority, these days a very reliable computer system, verifies transactions. In the case of spending money with a EVM chip credit card, five to ten seconds are spent communicating through the internet and verifying the transaction. The computers at Visa and Mastercard verify that the credit card is valid, and able to to spend the cash required.
Blockchain currencies require a similar communication, but with a decentralized database. If a seller can take payment in Bitcoin, they have a bitcoin account, or they have some bitcoin software on their computer. When they record the transaction, they must inform a consensus number of bitcoin pushers of the transaction, and if this command succeeds, the blockchain now records new transactions for both the payer and the payee.