What is the difference among horizontal detail coefficients, vertical detail coefficients and diagonal detail coefficients?

[Waterkin]

Hi, I was using dwt2 for a 3D time series with shape (Batch size, Time window, Feature Num).
However, I don't quite understand the difference among horizontal, vertical, and diagonal detail coefficients.
The doc did not explain it very explicitly.
Can anybody help me explain cH, cV, cD for a 3D time series?

[rgommers]

It would be helpful if you could point out the specific section(s) of the documentation that you looked at and that were close but not quite clear enough. That would help us fix them and hopefully answer your question in the process.