Blockchain is a dynamic system of storing data that anyone can access. Anytime there is a transaction on Blockchain, the system is updated automatically and visibly with the transaction data. NFTs live on the Blockchain and each time they are created, moved, or sold, that transaction is recorded. The benefit of Blockchain and why it’s considered so secure is that it’s only possible to add new transactions to the system.
No one can change or delete previous entries, so there is a permanent record that cannot be modified. There are several Blockchains (Cardano, Bitcoin, Ethereum, etc.), though no one company or person “owns” these chains. The way the data is stored is by peer-to-peer storage across huge numbers of computers rather than one centralized server. This ensures the data cannot be manipulated and is totally transparent.