The hippocampus, Latin for seahorse, is named for its shape. It is part of a system that directs many bodily functions: the limbic system. This system is located in the brain's medial temporal lobe, near the center of the brain.
The hippocampus is involved in the storage of long-term memory, which includes all past knowledge and experiences. Scientists are unsure exactly how this occurs. In particular, the hippocampus seems to play a major role in declarative memory, the type of memory involving things that can be purposely recalled, such as facts or events.
The hippocampus is not involved with short-term memory and procedural memory types (memory of how to do motor actions, like walking). These are primarily handled by the cortex and the cerebellum.
Those that have lost function or had removed major portions of the limbic system but still have the hippocampus, have only long-term memory and cannot record any new memories or functions.