Point-to-Point Tunneling Protocol - Definition from the Hotspot Shield Glossary
PPTP is a protocol used to expand networks through tunnels over the internet. PPTP is primarily implemented by large businesses to extend their own networks across the internet to incorporate other branches or offices for example so they can access the main network and share data etc. PPTP is mainly used in VPN’s and is instrumental in their creation, and ensures the security of data or messages being transferred from one node in a VPN network to another.
The PPTP protocol helps remote users of a corporation dial-in to the business network and means they do not have to physically be in the office for example. The tunneling aspect of the protocol refers to how one protocol is encapsulated within another, while the P2P aspect deals with their being two specific end points that need connecting.