Traditional Home Network
Typically, home networks were set up with one computer controlling access to the internet, either using NAT or proxy software.
It works great, except for the other computers to have internet access, the workstation needs to be on.
The workstation provides firewall protection for the network and depending on the sharing software used, you may have some control over the other computer's access to the internet.
Unless using ICS, you need to purchase software for sharing and for firewall.
Using A Router
With high-speed access becoming more popular and routers more affordable, the router can replace the workstation.
This allows any computer to access the internet irregardless of the status if the workstation.
The router provides firewall protection for the home network and can be easily be configured to block access for specific ports. For example, I can easily block all ports except 80 for only the computers my kids use.
No additional software is required.