My device is not rooted: I have rooted it before, but I did a full factory reset using the Nexus Factory Images. Root Checker tells me it's not rooted, and SuperSU tells me that it cannot find SU Binaries. However, when using multiple file managers, they can all see the '/' folder, and all the folders and files beneath it. I thought that root was required to do this. Is this correct, or am I imagining things? How can my device can see these? When actually going into Cheetah Mobile's File Manager Settings and checking the 'Root Explorer' option that apparently allows me to see the '/' folder, it says is cannot gain root access. How come multiple file managers let me see this folder? Thanks in advance.
I thought that root was required to do this.
That's not quite right. Any user can see that directory, but only root can write to it. Directories lower down the hierarchy such as
/data/data are not world-readable, so while you'll be able to see that that directory exists, you won't be able to see its contents on an unrooted device.
Some file managers choose not to offer the option to display system directories like the root directory unless the device is rooted, simply because it's not very useful to do so when you can't see the contents of some of its subdirectories or change it.