When would you use Multi-Row Formula rather than Summarize?

Summarize collapses rows into groups — the equivalent of SQL GROUP BY.

Multi-Row Formula keeps every row and can reference other rows with [Row-1:FieldName], which makes it the equivalent of a SQL window function. Running totals, period-over-period differences and filling values down all use it.

It depends on row order, so it needs a Sort before it, and it can be grouped by a field so the calculation resets per group.