PlayStation 2 online functionality

The PlayStation 2 home video game console has had the ability for online gaming and other Internet capabilities. Games that were online-compatible could make use of the feature using a network adapter that plugged into the system's Expansion Bay (the adapter is integrated into the hardware on later "slimline" models) and an Internet connection, which connected to one of Sony Computer Entertainment's or a third-party's network, depending on region.

Source: Wikipedia — PlayStation 2 online functionality (CC BY-SA 4.0)