What is a firewall and what are the different types of firewalls?

This video explains what a firewall is and what the different types of firewalls are. Interested viewers may find the following links useful:
Book: Cryptography And Public Key Infrastructure
www.thesecurit...
Book: Web Application Vulnerabilities And Prevention
www.thesecurit...
Book: A Guide To Cyber Security
www.thesecurit...
Cyber Security Courses - The Security Buddy
www.thesecurit...
All Articles on Cyber Security - The Security Buddy
www.thesecurit...
What is a firewall and how does it work? - The Security Buddy
www.thesecurit...
What is a Web Application Firewall (WAF)? - The Security Buddy
www.thesecurit...
Evolution of Firewalls: From Packet Filters to Next Generation Firewall (NGFW) - The Security Buddy
www.thesecurit...
What is Deep Packet Inspection (DPI)? - The Security Buddy
www.thesecurit...
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