Problem with Opening a File on my Desktop

[iMore Question]

I clik on a file on my desktop
A NEW WINDOW opens that is labelled the name of the file I clicked.
But inside the window on the left is a list Labeled FAVORITES: Google Drive, icloud Drive, Dropbox, Airdrop, Applications, Downloads, Desktop (this one is darkened) , Moveis, Music, Pictures, thie anotHer Labeled DEVICES with a list, ETC
THEN a SECOND COLUMN; with a list of all the files on my desktop, including the one i opened
THEN a THIRD COLUMN: with the contents of the file I opened.

until this phenonmena happened, only the contents of the file I opened would show up?
I want to go back to opening just the file

 

[Just_Me_D]

1. What type if computer? Mac, PC, Unix?
2. What OS? OS X, Windows, Linux?
3. What the of file?