What is the difference between a 32-bit and a 64-bit operating system?

Just out of interest really - because I have a 64-bit version of Windows 7, yet lots of programs like iTunes are for 32-bit. What is the difference, and does it have any real impact on how it runs etc.?

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…).