Wrapped tokens and bridges, explained
Why there is a version of Bitcoin on Ethereum, how bridges move value between chains, and why bridges are where the largest crypto losses have happened.
Blockchains cannot talk to each other. Bitcoin has no idea Ethereum exists. So when you see Bitcoin on Ethereum, you are not looking at Bitcoin — you are looking at a token that represents it.
What wrapping is
Someone locks real BTC with a custodian and issues an equivalent token on Ethereum. That token is wrapped Bitcoin. It is redeemable for the real thing, which is what gives it its value.
The same pattern explains most cross-chain assets. The wrapped token is a claim, and its worth depends entirely on whoever holds the locked original honouring it.
What a bridge is
A bridge automates that: lock an asset on one chain, mint a representation on another, and burn it to release the original. Some bridges are run by a company, some by a contract and a set of validators.
It is useful and it is the most dangerous construction in crypto. A bridge necessarily holds a large pool of locked assets, which makes it the single most valuable target on either chain, and several of the largest thefts in the industry's history have been bridge hacks.
Why this matters for ordinary transfers
Mostly it does not, and that is the point worth taking away. If you are moving USDT between wallets, pick the network both sides support and send natively. No bridge, no wrapping, no extra counterparty.
Bridges are for people who need an asset on a chain where it does not natively exist. If that is not you, the cheapest and safest route is the direct one.
A practical warning: a wrapped token and its original are different assets with different addresses. Sending wrapped USDT where plain USDT is expected fails the same way any wrong-asset transfer does.