Microsoft Certified Systems Engineer (MCSE) Question:

Packet Filtering Firewall:
This type of Firewall detects packets and block unnecessary packets and makes network traffic release.

Screening Router Firewalls:
It's a software base firewall available in Router provides only light filtering.

Computer-based Firewall:
It's a firewall stored in server with an existing Operating System like Windows and UNIX.

Hardware base Firewall:
Its device like box allows strong security from public network. Mostly used by big networks.

Proxy Server:
Proxy server allows all clients to access Internet with different access limits. Proxy server has its own firewall which filters the all packet from web server.