What does it mean when a film is rated R?

I'm english and i have just watched a trailer for public enemies and i am just wondering what the R means? Like what age you have to be and stuff? Is it like a 15 or an 18? I'm 17 btw.

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…).