Windows Explorer (also known as File Explorer in Windows 8 and later) is a very special program. In many ways, it “is Windows”, in that Windows Explorer is actually the program that’s responsible for displaying the task bar, the Start menu, the task-switcher, and a fair amount more.
Oh, and it’s also the program that you can use to browse around your hard disk to look at files and folders.
It’s definitely completely unrelated to Internet Explorer, but there is one characteristic that they share that can cause the kinds of problems you’re seeing.
They can both be extended.