The idea here is to use your mobile phone as a data communication device. Previously, some mobile phones had a built-in modem which let you connect to the Internet by hooking up your laptop to your mobile phone. This method utilized your mobile data service plans.
With the advent of 3G or HSDPA network, you can now easily hook up your laptop to the Internet via 3G. All you need to do is to set up your mobile phone and your laptop to communicate with each other. Your laptop will use your mobile phone 3G data network to get through the Internet. Unlike free WiFi, hooking up your laptop to the Internet using your mobile phone's 3G capability doesn't come cheap. The overall cost depends on how much your cellular data provider charges for airtime connectivity.