bridge: Hardware device used to connect multiple networks by passing packets. Can pass all data between networks or be set to selectively pass traffic by filtering certain packets.
firewall: Combination of hardware and software applications used to create a gateway and provide controlled access from an external network to an internal corporate or organizational network By reviewing all traffic and selectively allowing data to pass, the firewall protects the internal network from possible hostile action.
Copyright 1994 William H. Holt. Reprinted with permission from Unix: An Open Systems Dictionary, by William H. Holt & Rockie J. Morgan, published by Resolution Business Press.