Where is my data

Apologies if this has already been asked, I have search a numbe of topics and cannot find a question similar to mine. I have been using Power Bi for a little while but learn things as I go.

I am looking at a report that someone else has built but with no instructions or comments. More often that note, the data source is clear in the Advanced Editor let source = link to datawarehouse, sharepoint location etc. I have come across the following and not sure where the data source is:

let
Source = #"All Items",
#"Filtered Rows" = Table.SelectRows(Source, each ([type] <> "datetime"))
in
#"Filtered Rows"

If anyone could give me an insight into the query above, it would be greatly appreciated. I am assuming this is getting all data from a table called All Items where it is not a datetime field....but where is the table!!

Thanks