Caves are formed through various geological processes, including:

* Dissolution: The most common type of cave is formed by the dissolution of soluble rocks, like limestone, by acidic groundwater.

* Lava tubes: Caves can also be formed by flowing lava during volcanic eruptions.

* Erosion: Water and wind can erode rock, creating cavities that can develop into caves.

Let me know if you'd like to learn more about any specific type of cave or how they form!