Host Identity Protocol - Definition from the Hotspot Shield Glossary

This technology is used in IP networks to allow host identification; it separates the end point identifier of an IP address and the locator section; effectively this means that the host’s location is separated from its identity. HIP provides network mobility across the IP versions IPv4 and IPv6, and use useful for mobile computing systems and multihoming.

In traditional networks, data is routed using IP addresses - This can cause issues for mobile networks and devices that are not static in their location. HIP looks to move away from IP routing and uses end to end host identification instead - This is useful to protect from some types of Denial of Service (DoS) attacks and it also provides encryption.