When you visit a cryptocurrency exchange or DeFi application that supports Trezor hardware wallets, the website attempts to communicate with your device through Trezor Bridge. This software acts as a secure intermediary, translating web-based requests into commands your Trezor device understands.

The Trezor Bridge application continuously monitors for connected Trezor devices and maintains secure communication protocols. When a transaction requires signing, the bridge safely transmits the transaction details to your hardware wallet, where you can review and approve or reject the transaction directly on the device's screen.

This architecture ensures that even if your computer becomes compromised, your cryptocurrency remains secure because private keys never leave the Trezor hardware wallet. The bridge simply facilitates communication while maintaining the air-gapped security model that makes hardware wallets so effective.