What is a firewall? types of firewalls and using them?

I'm really confused on the difference between proxy server firewall.like many also the security server but the proxy server is divided into two parts to the application level and circuit-level gateway that I want to take the differece between the two and I also want the firewall on several levels. please give me my answer urgent soon.its

A firewall is a device or group of devices configured to permit, deny, encrypt, or proxy all computer traffic between different security domains. Comodo Firewall: http://www.comodo.com/products/free_products.html

Starcraft 2: Beginner Protoss Tactic – Proxy Gateway

Xtm 23W 3YR Utm Bundle Includes Firebox Appliance $1,815.19 WatchGuard XTM 23W VPN firewall appliance delivers performance-driven security to small business and remote sites that need strong protection without the hefty price tag. Enterprise-grade security includes full HTTPS content inspection and VoIP support. Wireless models feature dual-band 802.11n for WiFi with enhanced speed and responsiveness. Flexible, centralized management tools allow administra…

D-Link DI 714 – Wireless router – desktop …

Microsoft Forefront Threat Management Gateway (TMG) Administrator’s Companion (Pro -Administrator’s Campanion) $37.79 Get your Web security, network perimeter security, and application layer security gateway up and running smoothly. This indispensible, single-volume reference details the features and capabilities of Microsoft® Forefront® Threat Management Gateway (TMG). You’ll gain the real-world insights, implementation and configuration best practices, and management practices you need for on-the-job results….

IBM WebSphere DataPower SOA Appliance Handbook $48.48 Expert Guide to Deploying, Using, and Managing DataPower SOA Appliances IBM® WebSphere® DataPower® appliances can simplify SOA deployment, strengthen SOA security, enhance SOA performance, and dramatically improve SOA return on investment. In this book, a team of IBM’s leading experts show how to make the most of DataPower SOA appliances in any IT environment. The authors present …

ZTANGO UNVEILS CARRIER-GRADE WAP PUSH PROXY GATEWAY.(Company Business and Marketing): An article from: Telephone IP News $5.95 This digital document is an article from Telephone IP News, published by Worldwide Videotex on April 1, 2001. The length of the article is 642 words. The page length shown above is based on a typical 300-word page. The article is delivered in HTML format and is available in your Amazon.com Digital Locker immediately after purchase. You can view it with any web browser.Citation DetailsTitle: ZTANGO…