Tethering most commonly refers to using a mobile phone or other internet-connected mobile device to provide internet connectivity to a laptop or other computer.
Tethering can be physical or wireless. Physical tethering typically uses a USB cable to connect a mobile phone to a laptop. Wireless uses a Bluetooth connection instead.
Depending on the phone, computer, and mobile carrier involved, tethering may require software on the computer, and/or an app of some sort running on the mobile device to enable the connection. Similarly, not all mobile carriers include tethering as an option in all plans, and those that do will most often count the data transferred via a tethered connection against the mobile devices’ data plan.
Some mobile devices can be configured to be set up as WiFi hotspots. Very technically this isn’t really considered tethering, as the device is simply providing a wireless access point to any device that can connect to it. Tethering is more often used to refer to a dedicated computer-to-mobile device connection. However, since the functionality provided by using a mobile device such as a WiFi hotspot is so similar, misuse of the term is common.
Tethering, or phone-as-modem (PAM), is the sharing of a mobile device's Internet connection with other connected computers. Connection of a mobile device with other devices can be done over wireless LAN (Wi-Fi), over Bluetooth or by physical connection using a cable, for example through USB.
If tethering is done over WLAN, the feature may be branded as a personal hotspot or mobile hotspot, which allows the device to serve as a portable router. Mobile hotspots may be protected by a PIN or password. The Internet-connected mobile device can act as a portable wireless access point and router for devices connected to it.