Bridges do not physically move coins. The common lock-and-mint design holds your asset in a contract on the source chain and mints a wrapped-token on the destination. Burning the wrapped token releases the original.
What you hold after bridging is a claim, and its value depends entirely on the bridge remaining solvent and uncompromised. Newer designs use liquidity pools on both sides or validity proofs, each with different failure modes.
Practical points: confirm you selected the right destination network before sending, understand that a bridged asset and the native asset are different instruments that can trade apart, and never bridge more than you would lend unsecured to the bridge operator. See bridge-hack-risk.
Related: bridge-hack-risk, wrapped-token, sidechain, finality