A firewall is a type of security systems that can be either hardware or software. This can helps secure your network by acting as a gateway between your internal network and external traffic.
A firewall works as a gatekeeper or barrier between your computer and another network, such as the internet. It acts as a traffic controller, monitoring and filtering traffic attempting to enter your operating system. Firewalls protects your computer or network from outside cyber attackers by blocking out malicious or unnecessary network traffic. It can also prevent dangerous software from gaining access to a computer or network over the internet. Without a firewall, a business might quickly fall victim to a cyber-attack, leading it to lose all of the critical data.
Sources:
https://us.norton.com/internetsecurity-emerging-threats-what-is-firewall.html