The hippocampal-entorhinal system is central to both navigation and memory. Navigation relies on two mechanisms: map-based (allocentric) navigation, which uses spatial relationships between landmarks, and path integration (egocentric), which calculates position based on movement and previous locations. The hippocampus and entorhinal cortex support both navigation and memory, with grid cells, place cells, and head direction cells playing key roles in spatial representation. Semantic memory, which is independent of time, is similar to allocentric navigation, while episodic memory, which involves personal experiences, is linked to path integration. The hippocampus-entorhinal system enables the storage of numerous independent memories through its ability to generate complex, temporally evolving cell assemblies. Theta oscillations and grid cells contribute to spatial and temporal coding, with theta rhythms enabling the compression of time and space during memory recall. The system also supports the formation of mental 'travel' by internally generated sequences, allowing for the recall of past events and planning of future actions. The integration of these mechanisms suggests a common evolutionary basis for navigation and memory, with the hippocampal-entorhinal system playing a crucial role in both. Challenges remain in understanding the precise roles of different cell types and the mechanisms underlying memory and navigation.The hippocampal-entorhinal system is central to both navigation and memory. Navigation relies on two mechanisms: map-based (allocentric) navigation, which uses spatial relationships between landmarks, and path integration (egocentric), which calculates position based on movement and previous locations. The hippocampus and entorhinal cortex support both navigation and memory, with grid cells, place cells, and head direction cells playing key roles in spatial representation. Semantic memory, which is independent of time, is similar to allocentric navigation, while episodic memory, which involves personal experiences, is linked to path integration. The hippocampus-entorhinal system enables the storage of numerous independent memories through its ability to generate complex, temporally evolving cell assemblies. Theta oscillations and grid cells contribute to spatial and temporal coding, with theta rhythms enabling the compression of time and space during memory recall. The system also supports the formation of mental 'travel' by internally generated sequences, allowing for the recall of past events and planning of future actions. The integration of these mechanisms suggests a common evolutionary basis for navigation and memory, with the hippocampal-entorhinal system playing a crucial role in both. Challenges remain in understanding the precise roles of different cell types and the mechanisms underlying memory and navigation.