A blockchain is a shared database whose copy is held simultaneously by thousands of independent computers around the world. Transactions are packed into blocks, each block refers cryptographically to the previous one, and this produces a chain that could only be altered by recomputing every subsequent block at once across every copy. In practice that is impossible — which is where the defining property comes from: what is written stays written.
Why this matters to a casino player
Three practical consequences.
Your transfer is provable. Every deposit and withdrawal is a public record that anyone can inspect in a block explorer. In a dispute with a casino it is not your word against theirs — the transaction either exists or it does not.
A mistake is final. The same immutability that protects your transaction means money sent to the wrong address or on the wrong network cannot be recalled. A bank transfer has a reversal mechanism; a blockchain does not.
There is no anonymity. A blockchain is pseudonymous: an address does not carry your name, but the whole history of that address is public and stays public forever. If the address is ever linked to you, its entire history is linked to you retrospectively.
Different blockchains make different trade-offs between speed, fees and decentralisation — which is where the differences between the Bitcoin, Ethereum and Tron networks come from.