What is a VPN

A VPN is designed to provides a secure, encrypted tunnel in which to transmit the data between the remote user and the company network. The information transmitted between the two locations via the encrypted tunnel cannot be read by anyone else because the system contains several elements to secure both the company's private network and the outside network through which the remote user connects through.
The first step to security is usually a firewall between the client and the host server, requiring the remote user to establish an authenticated connection with the firewall. Encryption is also an important component of a secure VPN. Encryption works by having all data sent from one computer encrypted in such a way that only the computer it is sending to can decrypt the data.

A VPN alone is just a way to bolster your security and access resources on a network you're not physically connected to. What you choose to do with a VPN is a different story.

Uses for VPNs
VPNs are a fairly simple tool, but they can be used to do a wide variety of things:

Access a Business Network While Travelling
Access Your Home Network While Travelling
Hide Your Browsing Activity From Your Local Network and ISP
Downloading Files
and plenty of other reasons I have just mentioned just a few of them

For More information about VPN's have a look at http://iappsdevelopment.com/protectyourdata.aspx