What the file is a wordpress plugin that lets you see the files used in the construction of your wordpress site. This is useful for finding the files used on specific pages for editing purposes. The plugin works immediately upon installation, and subsequently accessed in the wordpress top bar (see below).
I used this plugin for finding the files that go into making up a wordpress page, so that I could edit specifics and change the formatting.
Used for locating the files containing standard wordpress components. They are edited in the themes files (in the menu : Appearance > Theme Editor).
Doesn’t show the functions used to create a lot of the code executed on site. These can be very hard to find.