ive got a HTC android, do you know how good the internet is through doing that?
Pretty much the same as using a 3G USB dongle, you can also place the phone where you want and could get a better 3G signal if it's poor in on location, it shares it's own 3G (assuming you have a 3G data tarrif) it uses the Wifi on it so more than 1 computer / laptop can connect to it at a time. On a HTC Android it's Menu, Settings, Wireless & networks, Portable wigi hotspot settings or in the Apps drawer you'll see Wi-fi Hotspot.
hth
PS: give yourself a password, don't leave it blank and remember to switch off the hotspot setting when you're not using it otherwise it'll drain your battery overnight, unless on charge.