AGR defines a multi-level BOM as a BOM in which items are both finished goods and components of something else, causing the BOM recipe to be more complex.
You can confirm which of your items are part of a multi-level BOM by filtering by
BOM component = 'Yes' and BOM parent = 'Yes'.
In the same Item Card, you might see 2 data series in the same forecast timeframe:
BOM Demand (to know how AGR derives it from the requirements of finished goods, check here)
Sales Plan (how much the item is expected to sell on its own, based on sales history patterns).
Both these data series are included in Total Demand, which is a key component in AGR's order calculations.