Quikoffice conundrum

[BWRpota]

(Please read the text bordered by ******* to avoid the detailed account of my methodology, for arriving at my final point.)
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What is "external SD" when choosing where to store a new .docx using Quikoffice? It seems to be a subfolder of "SD Card".

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1) I open Quickoffice.
2) I choose Quickword.
3) I choose SD Card for storage, then any desired subfolder.
4) I click the add document icon in the lower left corner of popup at the bottom of the screen.
5) I select "Word Document".
6) I create the document.
7) I click the far left softkey on the phone itself.
8) I select "Save As".
9) I clear the highlighted, "New Document.docx, then name the document.
10) Under, "Save In", I select SD Card.
11) I see a list of documents. AT THE VERY TOP IS, "EXTERNAL SD".
WHAT IS THAT?
If I select THAT, I GET A FEW SUBFOLDERS.
I click the Save button, and a view of the document I just saved returns.
What is "EXTERNAL SD" for?
The turning point is when I first see, "External SD" in the folder list. I can scroll on down and choose any pre-created folder.
What is " EXTERNAL SD"?