You Can Use Internet On Computer From Your Phone.

Tethering Mobile Data To Computer On iPhone

With iPhone, The tethering is allowed for certain phone models depending on the geography. You can go to settings > Personal mobile hotspot and then create a WiFi hotspot with which you can connect your WiFi devices to use the mobile data of your phone on your WiFi enabled laptops, tablets, gaming consoles and also other devices.

If your computer does not have WiFi, you can connect it via the data cable and install iTunes and enable USB tethering in the settings. In that case, an Ethernet adaptor will be created and you can use the mobile data via USB data cable.  more details here.

Tether Mobile Data To Computer On Android Phone

Now with Android phones, its much simpler to create a WiFi hotspot for tethering. Go simply to settings > Wireless Settings > More Settings > Portable WiFi Hotspot and enable the WiFi Hotspot or USB tethering as per the need of your's. 

Tethering Mobile Data To Computer On Feature Phones

For feature phones, you need to check whether the phone have 2G / 3G data capability and does it allow to connect to the PC like a modem. Most feature phones these days offer modem functionality. You need to install phone’s drivers and its modem drivers provided with the phone or downloaded from official website of the phone maker. Then you need to run the PC suit or the software for the particular phone and select the tethering or Modem option there. Better refer to the phone’s user’s manual as different brand of feature phones have different procedure of different phones to connect as modem.