What is wireless tethering

Tethering is the use of a mobile device such as a mobile phone to supply Internet access for another device which is otherwise unconnected, using the mobile device as a modem. This can be done through Bluetooth wireless technology, portable Wi-Fi hotspots, or cables (such as USB).

Tethering has been used to gain access to the Internet since mobile devices started using their networks to give users Internet access, but has increased in prevalence due to Internet connectivity in modern cell phones and laptops

source: wikipedia - wireless tethering