An exit relay is the final Tor node in a connection. It forwards traffic from the Tor network to the destination on the public internet, so the destination sees the relay’s IP address rather than the user’s. The relay does not automatically reveal the user’s identity, but it is a trust boundary because traffic leaves Tor there.
Exit relays can observe or alter traffic that is not protected by end-to-end encryption. HTTPS and other properly encrypted protocols protect content in transit, while unencrypted data may be readable to a hostile relay. For protocols such as SSH, encryption and careful verification of the server’s host key help prevent interception or impersonation. In defense, treat the exit relay as untrusted: use end-to-end encryption, heed certificate and host-key warnings, and avoid sending sensitive information through plaintext services.