Panning is an activity similar to fishing, where the player uses a tool (the pan) on bodies of water to collect nearly any ore type, some minerals, and (more rarely) other special items.
After a pan is acquired, 'shimmering lights' will begin to randomly spawn at shores and banks on any map, in a similar fashion as fishing spots. However, unlike fishing or other activites like foraging, panning doesn't have its own associated skill tree.