
Explanation:
Box 1: Inner -
Every Product has a ProductSubCategory.
A standard join is needed.
One of the join kinds available in the Merge dialog box in Power Query is an inner join, which brings in only matching rows from both the left and right tables.
Box 2: Left outer -
Not every ProductsubCategory has a parent ProductCategory.
One of the join kinds available in the Merge dialog box in Power Query is a left outer join, which keeps all the rows from the left table and brings in any matching rows from the right table.
Reference:https://docs.microsoft.com/en-us/power-query/merge-queries-inner https://docs.microsoft.com/en- us/power-query/merge-queries-left-outer