Understanding the syntax of Flatten

Questions
1

I humbly ask …

Is there a post somewhere that describes how the following syntax of Flatten works? I’m having trouble understanding this from what is described on the Flatten documentation page.

Flatten[list, { {s11,s12,...},{s21,s22, ...}, ...}]

flattens list by combining all levels sij to make each level i in the result

The related examples didn’t help my understanding.

Perhaps I’m also not understanding the meaning of Level 1, level 2, … and the concept of outermost, innermost.

2
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3

Ugh, the formatting didn’t turn out nice for browser viewing.

4

Thank you Eric.

Your description made sense, now I understand how the syntax of Flatten relates to where element wind up in the newly created list structure.

Helpful indeed !!