dead simple examples?

[end-user]

I'm struggling to understand how to perform row grouping. I've been looking at the examples, but the feature is mixed into examples that show many other features simultaneously. Are there any examples that show how to do just row grouping?

[end-user]

I think part of the problem is I don't understand the terminology that's being used or what it applies to. For example, I think both columns and rows can be both 'expanded' and 'grouped'. Creating column groups seems straightforward - you just nest the definitions and it creates a header that includes the nested columns. But I don't see anything similar for rows. Looking through the examples, it seems like what I want is an aggregated function, but in my use case, I don't actually want to aggregate anything.