Working out which type of network cable is which, and which cable to use when, can seem like a daunting task.  It's not. 

There are only two types of Ethernet cable, one of which you will use to connect your PlayStation®2 to your broadband Internet connection.  The rules for using network cables, and telling them apart, are very simple once you know them.

Straight through / CAT 5 / patch cable: The standard type of cable used to connect networks together is called a straight through cable.  It's also referred to by several other names, such as CAT 5 cable, network cable or patch cable, but they all refer to the same type of cable. These cables are mainly used to directly connect a piece of hardware to another piece of hardware in a network (hence, straight through.)  They use a specific kind of connector known as an RJ45 connector. 

If you are using a Direct Connection or Router Connection to connect your PlayStation 2 to your broadband Internet connection, then you will need at least one straight through cable.  This will be used to either connect your Network Adaptor to your Ethernet modem, or your Network Adaptor to your router. You cannot use a straight through cable to connect your PS2 directly to your PC, which you would need to do if you were using the Internet Connection Sharing connection type. To do that you need to use a crossover cable, which is detailed below.

Straight through cables are available from high street electronics or computer stores, web sites and independent retailers. They vary in length from one metre upwards, with very long lengths (70 metres plus) available. Usually, a straight through cable will not be labelled as a 'straight through cable' in a shop, or website, but will be referred to by one of the above names. However, a crossover cable will usually be clearly printed with 'crossover cable' on the packaging, so you shouldn't accidentally purchase the wrong type of cable. The rule of thumb is, unless your cable is labelled as a crossover cable, it's going to be a straight through cable.

Crossover Cable:
Crossover cables again use RJ45 connectors, and are designed to connect two computer systems directly together - or for our purposes, a PS2 and PC together.

Crossover cables should not be used when trying to connect your PS2 to hardware components like a hub, switch, router, or modem.  If you wish to connect a computer to one of those pieces of hardware then you should use a straight through cable, as detailed above.  If you are using an Internet Connection Sharing connection to connect your PlayStation®2 to your broadband Internet connection, then you will need one crossover cable, and possibly a straight through cable depending on your broadband connection.

You can tell a crossover cable from a straight through cable by holding the ends of the cable next to each other and examining the wires inside the RJ45 connector.  RJ45 connectors are usually transparent, so if you look closely at the inside of the connector you will see eight fine wires which are all different colours.  If the order (from left to right) in which the fine wires are placed inside of the connector is different between both connectors, then you have a crossover cable in your hands.  If the order of the fine wires inside the RJ45 connectors is the same for each end of the cable, it is a straight through cable.

Telephone cables are not network cables!
Telephones cables connect a telephone to a wall socket via connectors that look similar to RJ45 connectors, albeit smaller. These connectors are known as RJ11 connectors, and are unsuitable for connecting computer equipment together in a network.