EDIT: Thank you all for detailing your experience with, and hatred for, this miserable product. Your display of solidarity is inspiring. Now, say it with me:
The file/document integration is based on SharePoint. Shit built on top of a nice pile of manure
Edit: and don't get me started on the teams android app which requires access to all your media if you try to share a single image. If you share it as a file attachment however it's completely fine. No you're not getting access to my files and pictures MS, keep your filthy adware fingers off my data
Fun fact: internet explorer was originally built off the File Explorer.
I kinda stopped following programming for windows a decade ago. But in sure there is some ancient code from 30 years ago that is holding some critical files together.
Internet Explorer was originally based upon the Mosaic browser. Like a lot of Microsoft's tech, it's something they acquired.
Up to IE4, it was a standalone browser. It's IE4 where Microsoft integrated it into the OS and made do double duty as Windows Explorer, which is what you're thinking of.