Understanding BMLoops: Does every loop enclose a face?

I’m using bmesh to alter my geometry via python. Now I don’t seem to understand loops correctly. I thought that a BMLoop always covers the edges of a face as in it loops around it once. I can manouver back and forth between the next and previous loops via link_loop_previous/next and switch to adjacent face loops via link_loop_next_previous/next (order determined by the edge disks cycle around the loop vertex: https://wiki.blender.org/wiki/Source/Modeling/BMesh/Design)

But recently I stumbled upon a problem when i logged the loops that pass through a vertex which was the corner of a cube. The vertex had 4 loops. I don’t understand what face the fourth loop should belongs to? I’m maybe understanding it incorrectly.