Ubuntu’s Unity desktop comes in two versions. The first (default) one is called ‘Unity 3D’ and the second one is called ‘Unity 2D’. If you have a reasonably powerful graphics card and fancy having few 3d effects (smooth animations while window minimizing/restoring, drop shadows etc), then you should be using Unity 3D (it uses a program called ‘Compiz’ for creating those effects).
If you have an old VGA card and okay with not having few other ‘heavy’ 3D effects, then Unity-2d is not bad choice either. In fact, though they’re both designed using completely different UI tool-kits etc, Unity 2D developers have done extremely well thus it looks a lot like the 3D version, and unless you’re a bit experienced with Ubuntu, most can’t easily recognize the two desktops easily.
For instance, you can still know who’s who by having a look at the ‘Dash’, the menu that you get when right clicked on the ‘Trash’ icon, the look-n-feel of the Application launcher (application dock on the left-side of the desktop), window minimizing/restoring effects etc.
But who knows, in the future, Unity 2d might overcome those difference as well and might arrive at a point where it works and feels almost exactly as the Unity 3D thus making it more and more difficult to point out the differences and identify the two.
Anyhow, there are another two easy ways that you can use to identify whether you’re using Unity-2d or 3D in Ubuntu, using the command-line …
Method 1: You can search & find whether ‘Compiz’ is running from the desktop background, and if it exists, then it means that you’re definitely using Unity-3D because the 2D versions doesn’t use it.
For that, open your Terminal and enter the below command.
pgrep -l compiz
If it doesn’t find anything, then you’re running Unity 2D.
Method 2: Another way you can achieve the same thing is to search for ‘unity-2d’ using the above command (replacing ‘compiz’), because when Unity-2d desktop is running it runs two separate programs called ‘unity-2d-shell’ & ‘unity-2d-panel’.
So, after putting the below command if it finds those two programs, then it means that you’re running Unity-2D.
pgrep -l unity-2d
If it doesn’t find anything, then it means that you’re running the ‘fancy’ 3D version ;-).
Well, those are two ways that you use to identify the ‘two’ in Ubuntu Linux (if you know more ways, then I’m all ears :)).