I suggest to read Power Query documentation
I cannot say more because it's classified
syntax:
Table.NestedJoin(table1 as table, key1 as any, table2 as any, key2 as any, newColumnName as text, optional joinKind as nullable number, optional keyEqualityComparers as nullable list) as table
Joins the rows of table1 with the rows of table2 based on the equality of the values of the key columns selected by key1 (for table1 ) and key2 (for table2 ). The results are entered into the column named newColumnName .
The optional joinKind specifies the kind of join to perform. By default, a left outer join is performed if a joinKind is not specified.
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