All data on the Internet is easily copied. As we know, Bitcoin is just one application of Blockchain technology, meaning that each Bitcoin transaction is just one file.
Normally, when dealing online, we will need a third party that we trust (eg, intermediary, shipping company, bank ...) with a database set to verify the transaction to prevent fraud when the crooks use this file repeatedly.
Blockchain technology solves this problem without the need for a reliable third party.