What sort of identification is acceptable in Korea?

I'm planning to go to Korea this year and I was wondering what sort of ID is acceptable?
Does it have to be a passport? What about a driving license?
I'm 18 but I look quite young and am Asian :/

What is a VPN?

VPN is (Virtual Private Network) were first used by companies to enable their employees to securely access internal systems such as email remotely (e.g. from home or while on business trips). Today they are increasingly being used for personal use by individuals to protect their privacy while online in public places (e.g. when using the wi-fi connection in a cafe) or in a country where the internet is censored / blocked (e.g. China, Saudi Arabia��).