How to understand the weight w2d?

w2d : Shape (num_obj, num_points, 2)
I'm sorry, after reading papers and code for a long time, I still haven't understood the physical meaning of w2d.
For 2D matching, the weight is score: Shape (num_obj, num_points, 1), which represents the probability of matching between two pairs of 2d feature points. But why does this 3d-2d shape have two columns, and what is the specific meaning?
