Hi... extremely long character name
Dock apps or Slit apps is what you are looking for.
Gnome and KDE use a "System Try" to give you a look see at things that are running, but are more like "dummy" lights on a dashboard.
Here is one that you can run in "background" or "windowed" mode (actually windowed is the opposite of what is true)
gkrellm -w &
krells are those little applets that tell you system time, cpu info, HDD r/w's etc... Gkrellm is a Gtk wrapper for showing them in a nice window...
There are LOTS of docker apps like that...
That is one that you can use while in Gnome or KDE.
what you are probably referring to are window managers PLUS docker apps which give a nice transparent look to those apps running on a "clean" window manager.
Look up in Google for:
Blackbox <-- comes with RedHat
OpenBox 2 and now 3
I happen to like fluxbox. but it is only a window environment, and not a full window manager like KDE or Gnome (or is it the other way around??, hmmm) someone smarter than me can tell you that.
Anyhoo, I also am getting into the lovely niceties of setting up your own window manager... and it is not "easy" there is a LOT of reading to get into for it to run nicely and consistenly.
Warning: you are going to lose a lot of the functionality you have probably become used to if you are used to Gnome or KDE!!! These window managers are user dependent (read as difficult to get used and customize!) but are VERY fast, use very minimal system resources as opposed to bloated yet, more functional, environments such as KDE or Gnome.