With MS-DOS 4.0 in 1988, Microsoft began to move towards making DOS a little more user friendly. So they created DOS Shell as a more visual interface for people who did not or could not learn how to use the command line. Now folks could click on files and drag them between directories, or select file options from a drop-down menu. It could be configured as a two-pane file manager, with one pane over the other, but there is something about having identical left and right panels that is far more intuitive. No one ever learned to fly over the keys like a virtuoso pianist using DOS Shell like they could using its main competitor at the time, Norton Commander 2.0. DOS Shell also had a menu that could be configured to launch anything. Also, there's an option to view all the files on a disk, great for finding duplicates.
Starting with DOS 5.0 it contained a "task swapper" that could switch between multiple programs by swapping RAM to disk, but this was not true multi-tasking. When a program was swapped out it was frozen. Still, it was far more efficient than closing the program and starting it again. By the time MS-DOS 6.21 rolled out the MS-DOS SHell was no longer a core part of the distro, you had to ask Microsoft for a free supplemental disk to get it. Eventually it evolved into the Windows Explorer in Win95 onward, and development of the DOS Shell was dropped. This was about the time when everyone was moving to Windows 3.1, but for everyone who was left behind (like me) it was nice to have something approaching a decent graphical interface for DOS.
My laptop has enough RAM that I use three virtual RAM disks of 16 megabytes each, and DOS Shell uses one of these to swap programs. So system RAM is swapped to more RAM instead of a hard drive. That makes it blindingly fast. I have my budget spreadsheet and word processor and file manager and some games all active, and it's almost as easy as having multiple windows open under Windows. Also, this "Superman" color scheme is exactly how I like it.