Question about the data prepare functions in model.py

[limt15]

Thank you very much for sharing the fantastic code!
I wondered about the data format of the functionsquare_distance in the model.py script when I was reading it. Could you please tell more details of the input data below：

Input: src: source points, [B, N, C] dst: target points, [B, M, C]

What‘s the [B,N,C] and [B,M,C] looks like?
What’s the difference between the [B,M,C] and [B, npoint, C]?
And what‘s the means about these capital letters？