These are actual directories in your home folder. By default I believe it is:
The sidebar Has them laid out as shortcuts. All of these are inside of
So for example you CAN access these from the terminal by either doing
(or Pictures, Download,etc...) or by simply
To hide the sidebar
The simple way to get rid of them is to hide them. When you open files, if you move your mouse to the top bar and click "files" You can uncheck "Sidebar" and the sidebar will disappear.
That should make it look like this.
If you want to actually remove items from the sidebar you have to edit the
Editing the file
Open a terminal and use your go-to file editing program, since I use nano my commands will be based on it.
You will see lines containing
and so on for every directory (Documents, Pictures, etc.)
For the directories you would like to "remove" you have to change it to point simply at
After finishing changing whichever directories you want gone, use
ctrl-o to "write out" which means save, hit enter to save it, then
ctrl-x to exit the editor. After this, logout and log back in After you open files the directories should be gone. (In my test on 17.04 they showed up again as another category underneath where they were previously in the sidebar, simply right clicking and removing them seemed to work across multiple logouts)
I hope this helps.