The computers are connected to the switch or hub, which is connected to the router, or the firewall. Smartphones and tablets can also be included in a diagram.
This may be between your private network and the internet, your private network and your server, or different networks that are connected to each other.
Some firewalls also have antivirus software and threat detection built in.
They can be set to block or allow traffic based on state, port, or protocol. This can protect any network that is connected to the internet.