Map & timeline
Every photo carries embedded GPS metadata if the camera or phone that took it recorded location — most phones do this by default. PhotoShare reads that metadata on upload and plots each photo as a pin automatically, with no manual step required.
An album's map view is those pins aggregated: zoom out to see a whole trip at once, zoom in and individual photos cluster apart into their own markers. The timeline view uses the same underlying timestamp metadata, ordering photos chronologically regardless of which album they were uploaded to.
Photos without GPS data — a screenshot, an old scan, a photo with location services off — simply don't get a map pin, though they still appear in the timeline by timestamp. You can add a location to any photo manually afterward if you'd like it included on the map.