On the forums this is a topic that gets a lot of discussion and it can be confusing to someone new to computers and networking. Ports allow Internet traffic to be routed to specific device. This allows you to use Skype, for example, or perhaps to play an on-line game.
In many cases most people will not need to worry about this as Universal Plug and Play (UPnP) is used and a device will automatically log a port requirement with the router. However some devices will need the port to be manually configured. To benefit from this, the device in question will need a static IP Address as well.
An example might be a NAS (Network Attached Storage) which could store some files that you may want to access when away from home. By typing in your Internet IP Address (i.e. 22.214.171.124) with a suitable port number (i.e. 8080) you could than access the NAS when away from home in a browser or other program. In this example you could put in 126.96.36.199:8080 in your browser to access the NAS.
It is worth noting that if you are someone who is likely to access something on their home network when away from home, then you should consider using a 'Dynamic DNS Address' (a personal web address). The Internet IP Addresses issued to Sky's customers can change periodically and should not be thought of as fixed. This is known as having a 'Dynamic IP Address'. Setting up the DynDNS settings is discussed elsewhere in this publication. Essentially though you would type in the dynamic DNS address with the port number. For example:
Note: By using a consistent name, DynDNS will then redirect you to the current Internet IP Address of your router. Should your internet connection change its Internet IP Address, then the router will update the DynDNS register.
Some games and devices will require multiple ports to be opened. Some may be consecutive, others may be quite different. Essentially each port will be required to be opened either through UPnP or manually by amending the router.
The available port numbers range from 1 to 65535. Some are allocated to specific services whilst others are free to be used for whatever purpose you require. Please see the Wikipedia page linked below for more information on this:
One particular area where people commonly have issues is with games machines, such as the Xbox and PS/3. Please feel free to visit the forum for specific advice if you are having problems.
Port forwarding - What is Port forwarding about