What does this power query does?

[PowerrrBrrr]

I have a report and I am trying to understand the query written in there. This is one of the table which has been manually created and have columns "max" and "min" along with others. I dont understand what the below queries are doing. in one step there is a filtering with max as no null and then max as null and then there is merging but there is no 2nd table defined.

What is happening here?? Can someone explain?

#"Filtered Rows2" = Table.SelectRows(#"Changed Type", each ([max] <> null)),
#"Filtered Rows" = Table.SelectRows(#"Changed Type", each ([max] = null)),
#"Removed Columns" = Table.RemoveColumns(#"Filtered Rows",{"max", "min"}),
#"Merged Queries" = Table.NestedJoin(#"Removed Columns", {"source_ext_id"}, #"Filtered Rows2", {"source_ext_id"}, "max", JoinKind.LeftOuter),
#"Expanded max" = Table.ExpandTableColumn(#"Merged Queries", "max", {"max", "min"}, {"max", "min"}),

[amitchandak]

@PowerrrBrrr , there is merge (merge queries)happening in second last step and then in last step column Max and min are added to the current table 

Merge Tables (Power Query) : https://www.youtube.com/watch?v=zNrmbagO0Oo&list=PLPaNVDMhUXGaaqV92SBD5X2hk3TMNlHhb&index=16

[PowerrrBrrr]

I dont know what to say to you.. I know that there is merging happening, but as I mentioned in the question, i didnt get how and why the filtering is happening on max columns once for null and then without null and why and how this is getting merged.