What is a firewall in computing?

In computing, a firewall is hardware, software, or a combination of both that filters incoming and outgoing data traffic. It acts like a gatekeeper, allowing permitted connections and blocking suspicious or unwanted ones based on security rules. Firewalls can protect a single device, an office network, or a large data center. They are used alongside other defenses such as antivirus software, encryption, and authentication systems. Firewalls became especially important as internet-connected systems grew and cyberattacks became more common.