It’s a specialized window arrangement which is deeply tied to two aspects: the type of applications you use and whether you were able to adopt its paradigm. You’ll find it more often among programmers, scientists and researchers, writers, IT professionals, on stock markets, hospitals, airlines, factories…
At its core, titling window managers are a transposition of the traditional application layout onto the desktop. Looking at an application like, say, LibreOffice or an IDE, you’ll find their layout elements are tiled on the screen. This is of course a necessity. Tiling windows moves this paradigm out of the application and into the desktop. It follows the same idea of permitting quick access to different areas of the desktop (applications) and allowing for multiple applications to be viewed at the same time.
I have started to learn to appreciate the paradigm when I first felt the necessity to buy a second monitor. My motivation was not exactly to increase my desktop space, but to be able to see multiple applications at the same time. Essentially I needed to tile my monitors. Programming on one screen and having documentation opened on another, for instance. But it was only when I met Linux that I finally was able to experiment. The i3 Tiling WM was still on its infancy but quickly became my de facto desktop. For some reason I was able to quickly get into the paradigm. Others may not find it so easy.
Today I use it less often. My days of programming are over and I do it only as a sporadic hobby. But every time I do my math study and research and use the available software on Linux, that’s when I miss i3 greatly. With my move to Arch Linux however, I will have a chance to use it once more. I couldn’t quite ever get it to work nicely with Ubuntu.