Bridge
A system that moves value between two blockchains, usually by locking an asset on one and issuing a representation on the other.
Designs vary widely in what a user must trust: a federated bridge relies on a multisignature group holding the locked collateral, a light-client bridge verifies the source chain's consensus inside a contract on the destination chain, and a liquidity network avoids issuance entirely by having a counterparty pay out on the far side. The wrapped token a bridge issues is a claim on whatever is locked, so it is only as sound as that custody arrangement, and two wrapped versions of the same asset from different bridges are different tokens that do not substitute for each other. Because bridges concentrate large balances behind a single contract or key set, several of the largest exploits in the industry have been bridge exploits, including the Ronin and Wormhole incidents in 2022. Some issuers avoid the problem by burning and minting natively on each chain, so no locked collateral exists.
In practice
Native issuance schemes burn a stablecoin on one chain and mint it on another, so the amount in circulation stays constant and no bridge holds collateral.
The common misunderstanding
Bridging does not send the original coin to another chain; the original is locked or burned and a separate representation is created, which can lose its backing.